Sensors probes

Important notes

The following sections describe the main features and the general usage for all the sensors probes included in the Plug & Sense! Smart Water Xtreme model.

It is important to remark that Smart Water Xtreme is only available in the Waspmote Plug & Sense! line. It is not available for the Waspmote OEM line. Besides, keep in mind that Smart Water Xtreme is not compatible with the former Smart Water or Smart Water Ions models. In other words, the sensor probes described in this Guide are only compatible with Smart Water Xtreme, because its advanced electronics allow these specific sensor integrations (some exceptions are the BME, Ultrasound or Luminosity sensors). .

In order to keep this guide as short as possible, some manufacturer information has been omitted. Libelium encourages the reader to visit the manufacturer websites and to spend some time studying all the technical papers and application notes provided for each sensor. Measured parameters on the great majority of Smart Water applications require a deep knowledge and, what is a more, sophisticated measure techniques to obtain the best accuracy.

The importance of laboratory tests

Additionally, Libelium highly recommends to carry out comprehensive laboratory tests before installing the system on the field, as well as proof of concepts on the field during a reasonable period, before going to a real deploy. Thanks to these good practices, the user will have an idea of the platform behavior, which will be very close to the reality. Parameters like accuracy over time, signal drift or battery drain can be only measured with real tests. As a result, a lot of time will be saved.

Typical scenarios

The Smart Water Xtreme model integrates high end sensors valid for the great majority of smart water applications like fish farming, waste water management or drinking water monitoring. They are developed in a robust and compact design, making them waterproof and allowing to place them completely underwater during long periods. In fact, they should be immersed completely for a good measurement. Take into account if the volume of water changes, like the flow in rivers and canals or sea tides.

Deployment

However, the deployment of the sensor is a matter of concern. First, it is recommended to isolate the sensors from big solids, rocks, walls or any the animal life present to prevent physical damages to the sensor. Besides, they would have to be placed at certain distance from other objects like motors or water pumps, in order to minimize interferences with the measures. Second, variable water flows, bubbles, rapid temperature changes or some chemicals would be avoided as much as possible in order to improve the quality and stability of measures. There are some accessories and solutions to achieve a good installation. Incidentally, it must not be forgotten to store the sensors correctly if they are not going to be used for a certain period. In the following sections more information is given about it.

Maintenance

Always take into account a maintenance factor for each sensor probe. The environmental conditions could affect the sensor behavior and accuracy, therefore it will become mandatory a periodic maintenance for each sensor probe, to watch out things like dirty on sensor probes, measure position or wire connections. The period between these maintenance actions will be different on each application.

Calibration

One of the most striking issues is the difference between maintenance tasks and calibration processes. While maintenance is done by low profile technicians, calibration is done only by skilled engineers with the necessary knowledge about the sensors. Despite Plug & Sense! is a stand-alone device, the Smart Water Xtreme sensor probes will definitely require certain maintenance and calibration. A large number of tips and advices, besides than reference calibration and maintenance periods are given in each sensor section.

Even though manufacturers generally recommend a calibration before every measurement, it is not feasible at all when sensors are deployed in a remote location. Nevertheless, it is not really necessary unless an extremely accurate value is required, for a general purpose application a much more spread set of recalibrations should be enough.

This way, the frequency of the recalibration process will be determined by both the accuracy required in the given application and the environment in which the sensors will be operating. The more accurate measurements required, the more often will be necessary to recalibrate the sensor. As well, an aggressive environment with harmful chemicals or with an important variation of the conditions of the parameter under measurement and its temperature will lead to a faster loose of precision, while more steady conditions will allow the user to spread the recalibrations along time.

Life expectancy

If they are not subject to harassing environments Smart Water Xtreme sensor probes may keep on functioning for periods of several months, providing the required recalibrations are performed to maintain the accuracy demanded by the application.

It can be summarized that both recalibration and lifetime of the sensor probes depend on 3 main factors:

1. Water environment: corrosive chemicals, salt, dirt, extreme temperatures, strong flow currents decrease the lifetime.

2. Usage: the more the probes are used the sooner they need to be changed due to the depletion of the substances used as reference and measurement electrodes.

3. Time: event in perfect conditions and low usage, the chemical reactions that take place in the reference electrodes will stop working.

Owing to all that, the OPTOD and PHEHT sensor probes (or their consumable parts) will probably have to be replaced between 6 months and one year after they have been deployed. For the optic sensor probes NTU and MES5 and the CTZN, the period is longer. The process of replacement is really easy as the probes may be easily unscrewed using just the hand.

Also beware that if, as indicated before, the sensors are placed in a chemically or physically aggressive media, with for example temperatures close to the extremes of the operating range, extreme air humidity (especially near salty water), strong flow of water or with presence of corrosive chemicals or salt, these wear and depletion processes may accelerate thus severely shortening the life of the sensors. In case of doubt please contact Libelium to get support about the sensors' durability.

How to detect a non-working probe

There are certain symptoms that will reveal that a sensor is not working properly:

• A lack of a proper response during calibration process. This is an obvious error which may appear in different ways and in different degree. A noisy output of several millivolts when submerging the probes in the calibration solutions, inconsistent values with the expected output given in section "Calibration Procedure" and never reaching a stable output will be indicatives of a defective of probe.

• A steady continuous measurement for a long time. It is very rare that these sensors show a continuous value in a real environment as they do in laboratory. Owing to liquid flow, temperature effects or biological action, a slow fluctuation is to be expected. If the measurement is stalled in a given value, the probe will probably be broken.

• A sudden change in the output of the sensor. The sensors' reaction is not instantaneous, if there is a leap between two consecutive measurements a problem with the sensor may have occurred (this kind of error may not be detected if a long time takes place between measurements).

• Values out of range. If the sensor drifts out of the normal operation range it will probably be caused by a failure.

If there are doubts about the correct operation of the sensor it is recommended to carry out a new calibration in order to discard any possible malfunction.

In any case, please contact our Sales department through the next link if you require more information: https://www.libelium.com/contact.

New Sensors for Waspmote Plug & Sense! Smart Water Xtreme

Table 1: Parameters, units, ranges, resolutions and accuracies of every sensor

Sensor name	Parameters	Units	Range	Resolution	Accuracy
Aqualabo OPTOD	Temperature	degrees Celsius	0,00 to + 50,00 ºC	0,01 ºC	± 0,5 °C
Aqualabo OPTOD	Oxygen	% saturation	0,0 to 200,0 % SAT	0,1	± 1 %
Aqualabo OPTOD	Oxygen	mg/L	0,00 to 20,00 mg/L	0,01	± 0,1 mg/L
Aqualabo OPTOD	Oxygen	Ppm	0,00 to 20,00 ppm	0,01	±0,1 ppm
Aqualabo PHEHT	Temperature	degrees Celsius	0,00 to + 50,00 ºC	0,01 ºC	± 0,5 °C
Aqualabo PHEHT	pH	pH	0,00 to 14,00 pH	0,01 pH	± 0,1 pH
Aqualabo PHEHT	Redox (ORP)	mV	1000,0 to + 1000,0 mV	0,1mV	± 2 mV
Aqualabo PHEHT	pH	mV	-	-	-
Aqualabo C4E	Temperature	degrees Celsius	0,00 to + 50,00 ºC	0,01 ºC	± 0,5 °C
Aqualabo C4E	Conductivity	μS/cm	4 ranges to choose (or automatic): 0-200,0 μS/cm 0 –2000 μS/cm 0,00 –20,00 mS/cm 0,0 –200,0 mS/cm Automatic	0,01 to 1 according the range	± 1 % full range
Aqualabo C4E	Salinity	Ppt = g/Kg	5-60 g/kg	0,01 to 1 according the range	± 1 % full range
Aqualabo C4E	TDS – Kcl (Total dissolved solids)	ppm	0-133 000 ppm
Aqualabo NTU	Temperature	degrees Celsius	0,00 to + 50,00 ºC	0,01 ºC	± 0,5 °C
Aqualabo NTU	Nephelometric Turbidity	NTU	0-4000 NTU 4 ranges to choose for Parameters 1 and 2 (or automatic): range 1: 0 / 50 NTU (FNU) range 2: 0 / 200 NTU (FNU) range 3: 0 / 1000 NTU (FNU) range 4: 0 / 4000 NTU (FNU) -Automatic	0,01 to 1 NTU – mg/L	± < 5 % full range Range 1: ±2,5NTU Range 2: ±10NTU Range 3: ±50 NTU Range 4: ±200NTU
Aqualabo NTU	Nephelometric Turbidity	FNU (1 FNU = 1 NTU)	Same ranges than the previous parameter	0,01 to 1 NTU – mg/L	± < 5 % full range Range 1: ±2,5NTU Range 2: ±10NTU Range 3: ±50 NTU Range 4: ±200NTU
Aqualabo NTU	SS (Suspended Solids	mg/L	0 to 4500 mg/L	0,01 to 1 NTU – mg/L	± < 5 % full range Range 1: ±2,5NTU Range 2: ±10NTU Range 3: ±50 NTU Range 4: ±200NTU
Aqualabo CTZN	Temperature	degrees Celsius	0,00 to + 50,00 ºC	0,01 ºC	± 0,5 °C
Aqualabo CTZN	Conductivity	mS/cm	0,0 –100,0 mS/cm	0,1 mS/cm	Check dependency tables
Aqualabo CTZN	Salinity	Ppt = g/kg	5-60 g/kg	0,1 mS/cm	Check dependency tables
Aqualabo CTZN	Conductivity not compensated with temperature	mS/cm	0,0 –100,0 mS/cm	0,1 mS/cm	Check dependency tables
Aqualabo MES 5	Temperature	degrees Celsius	0,00 to + 50,00 ºC	0,01 ºC	± 0,5 °C
Aqualabo MES 5	Sludge blanket	%	0-100 %	0.01 to 0.1 %	0,02
Aqualabo MES 5	SS (Suspended Solids)	g/L	0-50 g/L	0.01 g/L	<10%
Aqualabo MES 5	Turbidity	FAU	0-400 FAU	0.01 to 1 FAU	0,05
Eureka Fluorometer: Chlorophyll a - blue	Chlorophyll a - blue	μg/l	0 to 500 μg/l	6 digits with maximum of two decimals	linearity of 0.99R²
Eureka Fluorometer: Chlorophyll a - red	Chlorophyll a - red	μg/l	>500 μg/l	6 digits with maximum of two decimals	linearity of 0.99R²
Eureka Fluorometer: Phycocyanin (freshwater BGA)	Phycocyanin (freshwater BGA)	ppb	0 to 40,000 ppb	6 digits with maximum of two decimals	linearity of 0.99R²
Eureka Fluorometer: Phycoerythrin (marine BGA)	Ammonium	ppb	0 to 750 ppb	6 digits with maximum of two decimals	linearity of 0.99R²
Eureka Fluorometer: CDOM/fDOM	CDOM/fDOM (Colored Dissolved Organic Matter/ Fluorescent Dissolved Organic Matter)	ppb	0 to 1250 or 0 to 5000 ppb	6 digits with maximum of two decimals	linearity of 0.99R²
Eureka Ion-selective electrodes (ISE's): Ammonium	Ammonium	mg/l	0 to 100 mg/l as nitrogen	0.1	5% or 2 mg/l
Eureka Ion-selective electrodes (ISE's): Nitrate	Nitrate	mg/l	0 to 100 mg/l as nitrogen	0.1	5% or 2 mg/l
Eureka Ion-selective electrodes (ISE's): Chloride	Chloride	mg/l	0 to 18,000 mg/l	0.1	5% or 2 mg/l
Eureka Ion-selective electrodes (ISE's): Sodium	Sodium	mg/l	0 to 20,000 mg/l	0.1	5% or 2 mg/l
Eureka Ion-selective electrodes (ISE's): Calcium	Calcium	mg/l	0 to 40,000 mg/l	0.1	5% or 2 mg/l

Table 2: Applications and measuring principlesTable 2: Applications and measuring principles

Sensor name	Parameters	Applications	Measuring principle
Aqualabo OPTOD	Temperature	Industrial and municipal sewage treatment plants	Optical measure by luminescence technology
Aqualabo OPTOD	Oxygen	Wastewater management (nitrification and de-nitrification) Surface water monitoring Fish farming, aquaculture Drinking water monitoring	Optical measure by luminescence technology
Aqualabo PHEHT	Temperature	Industrial and municipal sewage treatment plants	ORP: Platinum electrode - Ag/AgCl reference
Aqualabo PHEHT	pH	Wastewater management (nitrification and de-nitrification)	PH: plasticized PONSEL
Aqualabo PHEHT	Redox (ORP)	Surface water monitoring
Aqualabo PHEHT	pH	Drinking water monitoring	PLASTOGEL®. Electrolyte – Ag/ AgCl reference
Aqualabo C4E	Temperature	Industrial and municipal sewage treatment plants
Aqualabo C4E	Conductivity	Wastewater management (nitrification and de-nitrification)*	Electrochemical conductivity sensor with 4 electrodes (2 graphite, 2 platinum)
Aqualabo C4E	Salinity	Surface water monitoring
Aqualabo C4E	TDS – Kcl (Total dissolved solids)	Drinking water monitoring
Aqualabo NTU	Temperature	Urban wastewater treatment (inlet/ outlet controls)
Aqualabo NTU	Nephelometric Turbidity	Sanitation network Industrial effluent treatment	Nephelometry: Optical IR (850 nm) sensor based on IR diffusion at 90 degrees
Aqualabo NTU	SS (Suspended Solids)	Surface water monitoring Drinking water
Aqualabo CTZN	Temperature	Urban wastewater treatment
Aqualabo CTZN	Conductivity	Industrial effluent treatment	Inductive conductivity sensor regulated in temperature
Aqualabo CTZN	Salinity	Surface water monitoring
Aqualabo CTZN	Conductivity not compensated with temperature	Sea water Fish farming
Aqualabo MES 5	Temperature	Urban Waste water treatment (Inlet/ sewage water (SS, Turbidity), Aeration basin (SS), Outlet (Turbidity)
Aqualabo MES 5	Sludge blanket	Treatment of industrial effluents (Aeration b asin (SS)), Clarifier (Sludge blanket), Outlet (Turbidity)	Absorptometry: Optical IR (870 nm) sensor based on IR absorption at 180 degrees
Aqualabo MES 5	SS (Suspended Solids)	Sludge treatment (Centrifugation)
Aqualabo MES 5	Turbidity	Dredging site (turbidity)
Eureka Fluorometer: Chlorophyll a - blue	Chlorophyll a - blue	lakes, rivers, ground water... oceanographic process waters waste waters laboratory research	Turner Designs fluorometric sensors, with each tuned to the slightly different wavelengths. Fluorometric sensors emit light at a certain wavelength, and look for a very specific, different wavelength in return. The magnitude of the return light is relatable to the amount of analyte present.
Eureka Fluorometer: Chlorophyll a - red	Chlorophyll a - red	lakes, rivers, ground water... oceanographic process waters waste waters laboratory research	Turner Designs fluorometric sensors, with each tuned to the slightly different wavelengths. Fluorometric sensors emit light at a certain wavelength, and look for a very specific, different wavelength in return. The magnitude of the return light is relatable to the amount of analyte present.
Eureka Fluorometer: Phycocyanin (freshwater BGA)	Phycocyanin (freshwater BGA)	lakes, rivers, ground water... oceanographic process waters waste waters laboratory research	Turner Designs fluorometric sensors, with each tuned to the slightly different wavelengths. Fluorometric sensors emit light at a certain wavelength, and look for a very specific, different wavelength in return. The magnitude of the return light is relatable to the amount of analyte present
Eureka Fluorometer: Phycoerythrin (marine BGA)	Ammonium	lakes, rivers, ground water... oceanographic process waters waste waters laboratory research	Turner Designs fluorometric sensors, with each tuned to the slightly different wavelengths. Fluorometric sensors emit light at a certain wavelength, and look for a very specific, different wavelength in return. The magnitude of the return light is relatable to the amount of analyte present.
Eureka Fluorometer: CDOM/fDOM	CDOM/fDOM (Colored Dissolved Organic Matter/ Fluorescent Dissolved Organic Matter)	lakes, rivers, ground water... oceanographic process waters waste waters laboratory research	Turner Designs fluorometric sensors, with each tuned to the slightly different wavelengths. Fluorometric sensors emit light at a certain wavelength, and look for a very specific, different wavelength in return. The magnitude of the return light is relatable to the amount of analyte present.
Eureka Ion-selective electrodes (ISE's): Ammonium	Ammonium	lakes, rivers, ground water... oceanographic process waters waste waters laboratory research	Membrane that is selective for the analyte of ammonium. The electrode’s filling solution contains a salt of the analyte, and the difference between that salt’s concentration and the analyte concentration in the measured water produces a charge separation. That charge separation is measured, relative to the reference electrode, as a voltage that changes predictably with changes in the analyte concentration in the water adjacent the membrane.
Eureka Ion-selective electrodes (ISE's): Nitrate	Nitrate	lakes, rivers, ground water... oceanographic process waters waste waters laboratory research	Membrane that is selective for the analyte of nitrate. The electrode’s filling solution contains a salt of the analyte, and the difference between that salt’s concentration and the analyte concentration in the measured water produces a charge separation. That charge separation is measured, relative to the reference electrode, as a voltage that changes predictably with changes in the analyte concentration in the water adjacent the membrane.
Eureka Ion-selective electrodes (ISE's): Chloride	Chloride	lakes, rivers, ground water... oceanographic process waters waste waters laboratory research	Membrane that is selective for the analyte of chloride. The electrode’s filling solution contains a salt of the analyte, and the difference between that salt’s concentration and the analyte concentration in the measured water produces a charge separation. That charge separation is measured, relative to the reference electrode, as a voltage that changes predictably with changes in the analyte concentration in the water adjacent the membrane.
Eureka Ion-selective electrodes (ISE's): Sodium	Sodium	lakes, rivers, ground water... oceanographic process waters waste waters laboratory research	Membrane that is selective for the analyte of sodium. The electrode’s filling solution contains a salt of the analyte, and the difference between that salt’s concentration and the analyte concentration in the measured water produces a charge separation. That charge separation is measured, relative to the reference electrode, as a voltage that changes predictably with changes in the analyte concentration in the water adjacent the membrane.
Eureka Ion-selective electrodes (ISE's): Calcium	Calcium	lakes, rivers, ground water... oceanographic process waters waste waters laboratory research	Membrane that is selective for the analyte of calcium. The electrode’s filling solution contains a salt of the analyte, and the difference between that salt’s concentration and the analyte concentration in the measured water produces a charge separation. That charge separation is measured, relative to the reference electrode, as a voltage that changes predictably with changes in the analyte concentration in the water adjacent the membrane.

Optical dissolved oxygen and temperature OPTOD sensor probe

The Optical dissolved oxygen and temperature OPTOD sensor probe, based on a luminescent optical technology, meets the demands of long term smart water applications. The OPTOD sensor probe measures accurately without oxygen consumption, especially with very low concentrations and very weak water flow. It is designed in a compact, robust and light probe with a stainless steel body.

It is often recommended to use an atmospheric pressure sensor together with the OPTOD sensor probe, due to the degree of solubility of oxygen in water is dependant on the atmospheric pressure. Moreover, the salinity is also related.

Figure: Optical dissolved oxygen and temperature OPTOD sensor probe

Specifications

Dissolved oxygen sensor:

Technology: Optical luminescence Ranges:

• 0 to 20.00 mg/L

• 0 to 20.00 ppm

• 0 -- 200%

Resolution: 0.01 Accuracy:

• ±0.1 mg/L

• ±0.1 ppm

• ±1%

Response time: 90% of the value in less than 60 seconds Frequency of recommended measure: > 5 s Cross sensitivity: Organic solvents, such as acetone, toluene, chloroform or methylene chloride. Chlorine gas.

Temperature sensor:

Technology: NTC Range: 0 °C to +50 °C Resolution: 0.01 °C Accuracy: ±0.5 °C Response time: < 5 s

Common:

Water flow is not necessary Default cable length: 15 m Maximum pressure: 5 bars Body material: Stainless steel (titanium option available on demand for sea water applications) IP classification: IP68 Storage temperature: -10 °C to +60 °C

Figure: Sensor probe parts: (1) membrane cap (consumable), (2) membrane screw and seal, (3) sensor body

Figure: Dimensions of the OPTOD sensor probe

Measurement process

The OPTOD sensor probe provides a digital signal using the SDI-12 protocol.

Reading code:

{
    // 1. Declare an object for the sensor
    Aqualabo_OPTOD mySensor(XTR_SOCKET_A);
    // 2. Turn ON the sensor
    mySensor.ON();
    // 3. Read the sensor. Values stored in class variables
    // Check complete code example for details
    mySensor.read();
    // 4. Turn off the sensor
    mySensor.OFF();
}

During the sensor measurement, there is a small stabilization time of a few seconds, so it is recommendable to wait until the values remain stable over time.

A complete example code for reading this sensor probe can be found in the following link: https://development.libelium.com/sw-xtr-06-optod-sensor-reading

Socket

Connect the OPTOD sensor probe to Plug & Sense! Smart Water Xtreme in any of the sockets shown in the image below.

Figure: Available sockets for the OPTOD sensor probe

Maintenance

Calibration

By default, the sensor probe is factory-calibrated, therefore calibration may not be needed for the first usage. However, to increase the sensor accuracy if deviations are detected, calibration would be necessary. Nevertheless, before carrying out the sensor probe calibration, please bear in mind the next comments:

• The OPTOD sensor probe comes dry and it needs to be rehydrated for 12 hours in tap water before taking any measure.

• The sensor and the buffer solutions must have the same temperature, so before starting the calibration process leave all the necessary elements in the same temperature conditions. Besides, wait for sensor temperature stabilization once it has been immersed.

• During the sensor measurement, there is a small stabilization time of some seconds, so please wait until the values remain stable over time.

• The buffer solution bottles must be closed properly after the usage, to prevent deviations on the default values.

• The measured value for dissolved oxygen is automatically compensated with the temperature, air pressure, and salinity (salt content).

• It is recommended to replace the membrane every 2 years.

The sensor membrane must not be inside the dissolved oxygen buffer solution for more than an hour. Otherwise, it will be damaged and measures will be incorrect. Besides, some chemicals can damage the membrane. Contact our Sales department through the next link if you require more information: http://www.libelium.com/contact.

First of all, ensure that all necessary elements are present. It is important that if a calibration process is started, it should be completed to save the results in the sensor internal memory. Do not abandon the calibration process and always follow the given steps and guidelines to avoid a sensor misconfiguration. If the process needs to be repeated or abandoned, always type the 'Q' command to exit the calibration procedure.

Libelium provides the necessary standard buffer solution to calibrate the Smart Water Xtreme sensor probes. Refer to the calibration solution section for more information.

Figure: Necessary elements for the OPTOD sensor probe calibration

The sensor calibration can be done only on socket E. Owing to that, connect the sensor probe to socket E of the Plug & Sense! Smart Water Xtreme unit to calibrate the sensor, as shown in the image below. Do not use any other Plug & Sense! socket to calibrate a sensor. It will not work.

Figure: Connecting the sensor to the calibration socket

The OPTOD sensor probe allows to calibrate temperature and dissolved oxygen. Please read below the necessary steps to calibrate each parameter.

Temperature calibration

The temperature calibration process is the same for all Plug & Sense! Smart Water Xtreme sensor probes.

It is recommended to calibrate in 2 points. The user can choose any 2 points inside the sensor range, but it is recommended to use 0 ºC (can be achieved using water plus ice) and 25 ºC. Moreover, it is necessary to use an external thermometer as a reference.

Now, upload the temperature calibration example for the corresponding sensor probe. The code uses the serial monitor to assist the user with messages and recommendations. The main steps are described below, but the full details are provided in the code.

Step 1: Type the first calibration point (offset) on the serial monitor and press enter.

Figure: Type the first calibration point on the serial monitor

Step 2: Pour tap water in a clean beaker. Immerse the sensor in water at your selected offset. Remove the black protection cap before immersing the sensor in the buffer solution. Wait until values are stabilized over time and type 'N' to continue. Ensure there are not any bubbles on the sensor membrane to avoid measure disturbances.

Do not discard the black protection cap and keep it for the future. It will be useful if the sensor needs to be stored for a large period.

Figure: Immersing the sensor inside the calibration buffer solution

Step 3: Type the second calibration point (slope) on the serial monitor and press enter.

Figure: Type the second calibration point on the serial monitor

Step 4: Immerse the sensor in water at your selected slope. Wait until values are stabilized over time and type 'N' to continue.

Step 5: Save calibration data into the sensor by typing operators name and date of calibration. Then, the sensor values will be printed on the screen to check if the measures are done correctly.

Figure: Save the calibration data

Dissolved Oxygen calibration

The OPTOD sensor probe allows to calibrate the dissolved oxygen parameter with one or two calibration points. It is recommended that temperature and air pressure remain constant during the calibration process.

Upload the dissolved oxygen calibration example for the OPTOD sensor probe. The code uses the serial monitor to assist the user with messages and recommendations. The main steps are described below, but the full details are provided in the code.

Two points calibration:

With this method, a 0% concentration (offset) and a 100% concentration (slope) are measured, offering great accuracy for small concentrations.

Step 1: Type the desired number of calibration points on the serial monitor and press enter. After that, the first calibration point is automatically set to zero.

Step 2: Pour enough buffer solution in a clean baker to cover the sensor head. Immerse the sensor in the 0% standard buffer solution. Remove the black protection cap before immersing the sensor in the buffer solution. Remove the solution with the sensor so that the oxygen saturation decreases more quickly. Ensure there are not any bubbles on the sensor membrane to avoid measure disturbances. Wait until values are stabilized over time and type 'N' to continue.

Figure: Waiting for stabilization

The sensor membrane must not be in contact with the 0% buffer solution for more than an hour, so minimize the contacting time. Otherwise the membrane will be damaged permanently and incorrect measurements will be obtained.

Figure: Immersing the sensor inside the calibration buffer solution

Step 3: Remove the sensor from the buffer solution and clean it carefully as previously described.

Step 4: Now the second calibration point of 100% can be achieved by placing the sensor approximately 2 centimeters above the water surface and keeping the membrane without water drops that could disturb the measure. Remember to shake the water in order to introduce the maximum amount of oxygen inside water. The next picture shows a diagram.

Figure: Placing the sensor to achieve 100% of dissolved oxygen

Step 5: Wait until values are stabilized over time and type 'N' to continue.

Step 6: Save calibration data into the sensor by typing operator's name and date of calibration. Then, the sensor values will be printed on the screen to check if the measures are done correctly.

Figure: Save the calibration data

One point calibration:

It consists of measuring the 100% of dissolved oxygen as described previously. The one point calibration process is valid for most situations, especially on the field. Remember that any water droplets present in the membrane could distort the measures.

Cleaning the sensor

The OPTOD sensor probe is designed for low maintenance. However, it needs to be cleaned periodically to remove the possible fouling or other biologic material that could appear in the sensor.

Use tap water, soap to rinse the sensor carefully and a soft towel to dry it and remove the biological material.

Figure: Cleaning the sensor probe

The presence of biofilm in the sensor membrane can introduce measuring errors. Use a soft sponge if needed.

It is not necessary to remove the membrane for sensor cleaning.

Finally, if the sensor is not going to be used during a large period, it is important to clean the sensor prior to storing it. Remember to place the protection cap together with a moisture absorbent element (like a piece of cotton).

Installation

It is important to think about a few aspects before installing the sensor on the field:

• The sensor body should be easily accessible for cleaning, regular maintenance and calibration.

• The sensor body must be firmly fastened to avoid sensor swing and possible collisions with the surrounding objects that can damage the sensor.

• If the sensor is installed totally immersed, it should be fastened from the body and not from the cable. The cable is not designed to hold the sensor and it could be damaged.

• Avoid bubbles around the sensor.

• For those users interested in measuring directly inside pipes, there are pipe segments with a protected measurement point. As an optional accessory for this sensor, Libelium offers a pipe mounting adapter (available in PVC and in stainless steel) that can be connected to those special pipe segments.

Figure: Typical installation on a pipe

Figure: Another typical installation on a lake

If the sensor is used in a hard environment where animals, solids or other environmental elements can damage the sensor, a protection strainer is available as an accessory of extra protection. Contact our Sales department through the next link if you require more information: http://www.libelium.com/contact.

Figure: Protection strainer accessory

A complete sensor manual can be found on the manufacturer's website.

Application examples

• Industrial and public sewage treatment plants

• Wastewater management (nitrification and de-nitrification)

• Surface water monitoring

• Fish farming, aquaculture

• Drinking water monitoring

Calibration report

Together with this sensor we provide a factory calibration report in which the manufacturer ensures that the sensor has passed a calibration procedure with traceability.

pH, ORP and temperature PHEHT sensor probe

The pH, ORP and temperature PHEHT sensor probe combines 3 sensors in one probe, which has been designed to measure under hard conditions like pure snow melting water with low conductivity, lakes, rivers, sea water or even waste waters with high conductivity values.

The PHEHT sensor probe is based on measuring the difference of potential between a reference electrode and a measuring electrode. It includes a long-life reference which increases its lifetime and also it has a high interference immunity. The ORP sensor is thought for normal or modest accuracy applications (fine accuracy is not provided).

Besides, the sensor has a temperature compensation for pH measures carried out by its internal NTC temperature sensor.

Oxidation reduction potential (ORP) and Reduction / Oxidation (Redox) are equivalent terms.

Figure: pH, ORP and temperature PHEHT sensor probe

Specifications

pH sensor:

Technology: Combined electrode Measurement range: 0~14 pH Resolution: 0.01 pH Accuracy: ±0.1 pH

ORP sensor:

Technology: Combined electrode Measurement range: -1000 to +1000 mV Resolution: 0.1 mV Accuracy: ±2 mV

Temperature sensor:

Technology: NTC Range: 0 °C to +50 °C Resolution: 0.01 °C Accuracy: ±0.5 °C Response time: < 5 s

Common:

Default cable length: 15 m Maximum pressure: 5 bars IP classification: IP68 Storage temperature: 0 °C to +60 °C

Figure: Sensor parts: (1) protection strainer, (2) cartridge (consumable part), (3) clamp, (4) sensor body

Figure: Dimensions of the PHEHT sensor probe

Measurement process

The PHEHT sensor provides a digital signal using the SDI-12 protocol.

Reading code:

{
    // 1. Declare an object for the sensor
    Aqualabo_PHEHT mySensor(XTR_SOCKET_A);
    // 2. Turn ON the sensor
    mySensor.ON();
    // 3. Read the sensor. Values stored in class variables
    // Check complete code example for details
    mySensor.read();
    // 4. Turn off the sensor
    mySensor.OFF();
}

During the sensor measurement, there is a small stabilization time of a few seconds, so it is recommendable to wait until the values remain stable over time.

You can find a complete example code for reading this sensor probe in the following link: https://development.libelium.com/sw-xtr-10-pheht-sensor-reading

Socket

Connect the PHEHT sensor probe to Plug & Sense! Smart Water Xtreme in any of the sockets shown in the image below.

Figure: Available sockets for the PHEHT sensor probe

Maintenance

Calibration

By default, the sensor is factory-calibrated, therefore calibration may not be needed for the first usage. However, to increase the sensor accuracy if deviations are detected, calibration would be necessary. Nevertheless, before carrying out the sensor calibration, please bear in mind the next comments:

• The PHEHT sensor probe comes dry and needs to be rehydrated for 12 hours in a standard pH4 buffer solution before taking any measure.

• During the calibration process the temperature is not compensated, therefore it must be taken into account. On the contrary, during normal measures the temperature is compensated.

• It is important that the sensor and the buffer solutions have the same temperature, so before starting the calibration process leave all the necessary elements in the same temperature conditions. Besides, wait for sensor temperature stabilization once it has been immersed.

• During the sensor measurement, there is a small stabilization time of a few seconds, so please wait until the values remain stable over time.

• The calibration must be done every 15 days to get a reasonable accuracy in the measurements. However, depending on the application, the time between two calibrations would vary. It is highly recommended to do a test as close as possible to the conditions of the final application to check the sensor drift over time. This will allow adjusting the calibration periods according to the required accuracy.

• The buffer solution bottles must be closed properly after usage, to prevent deviations on the default values.

Do not place the sensor in distilled water. The sensor will be seriously damaged. Besides, the glass electrode is vulnerable to chemicals like organic solvents, acids and strong bases, peroxide and hydrocarbons.

First of all, ensure that all necessary elements are present. It is important that if a calibration process is started, it should be completed to save the results in the sensor internal memory. Do not abandon the calibration process and always follow the given steps and guidelines to avoid a sensor misconfiguration. If the process needs to be repeated or abandoned, always type the 'Q' command to exit the calibration procedure.

Libelium provides the necessary standard buffer solution to calibrate the Smart Water Xtreme sensor probes. Refer to the calibration solution section for more information.

Figure: Necessary elements for the PHEHT sensor probe calibration

The sensor calibration can be done only on socket E. Owing to that, connect the sensor probe to socket E of the Plug & Sense! Smart Water Xtreme unit to calibrate the sensor, as shown in the image below. Do not use any other Plug & Sense! socket to calibrate a sensor. It will not work.

Figure: Connecting the sensor to the calibration socket

The PHEHT sensor probe allows to calibrate temperature, pH and also check the ORP values. Please read below the necessary steps to calibrate each parameter.

Temperature calibration

The temperature calibration process is the same for all Plug & Sense! Smart Water Xtreme sensor probes. Refer to the previously described temperature calibration section of the OPTOD sensor probe for details.

pH calibration

In the same way as temperature, a two-point calibration is recommended for pH sensor of the PHEHT sensor probe. The offset and slope points can be achieved with the standard buffer solutions provided by Libelium. This calibration method offers the greatest possible level of accuracy and is particularly recommended.

In addition, it is recommended to calibrate first with pH 7 buffer solution and then move to pH 4 or pH 10 depending the range of the measures of the application.

It is important to remark that during the pH calibration process the temperature is not compensated and the pH value for standard buffer solution varies with the temperature, so it is important to carry out the calibration at 25 ºC. If it is not possible, take into account the next tables for temperature compensation. For example, if the buffer solution temperature is 20 ºC, the pH value will be 7.03 instead of 7.01.

Temperature (Celsius)	pH value for standard buffer solution	pH value for standard buffer solution
0	7.13	4.01
5	7.10	4.00
10	7.07	4.00
15	7.04	4.00
20	7.03	4.00
25	7.01	4.01
30	7.00	4.02
35	6.99	4.03
40	6.98	4.04
45	6.98	4.05

Figure: Temperature compensation table for standard buffer solutions

Upload the pH calibration example for the PHEHT sensor probe. The code uses the serial monitor to assist the user with messages and recommendations. The main steps are described below, but the full details are provided in the code.

Step 1: The pH calibration process allows 2 or 3 calibration points. Select the desired points.

Step 2: Type the first calibration point (offset) on the serial monitor and press enter.

Figure: Type the first calibration point on the serial monitor

Step 3: Pour enough buffer solution in a clean baker to cover the sensor head. Immerse the sensor in the pH 7 standard buffer solution. Remove the black protection cap before immersing the sensor in the buffer solution. Wait until values are stabilized over time and type 'N' to continue. The stabilization time for pH measures could take up to 20 minutes.

Do not discard the black protection cap and keep it for the future. It will be useful if the sensor needs to be stored for a large period.

Figure: Immersing the sensor inside the calibration buffer solution

Step 4: Remove the sensor from the buffer solution and clean it carefully as previously described.

Step 5: Type the second calibration point (slope) on the serial monitor and press enter.

Figure: Type the second calibration point on the serial monitor

Step 6: Pour enough buffer solution in a clean baker to cover the sensor head. Immerse the sensor inside the desired standard buffer solution. Wait until values are stabilized over time and type 'N' to continue.

Step 7: Save calibration data into the sensor by typing operator's name and date of calibration. Then, the sensor values will be printed on the screen to check if the measures are done correctly.

Figure: Save the calibration data

ORP calibration

Regarding the ORP calibration, it is done using a two-point calibration. The offset will be the zero value exposing the sensor in the air and the slope will be an ORP standard buffer solution (240 mV).

Upload the ORP calibration example for the PHEHT sensor probe. The code uses the serial monitor to assist the user with messages and recommendations. The main steps are described below, but the full details are provided in the code.

Step 1: The first calibration point (offset) is set to zero and it cannot be changed. So keep the sensor exposed to the air and wait till measure stabilization over time. Then type 'N' to continue. Remember to remove the black protection cap.

Do not discard the black protection cap and keep it for the future. It will be useful if the sensor needs to be stored for a large period

Step 2: Type the second calibration point (slope) on the serial monitor and press enter.

Step 3: Pour enough buffer solution in a clean baker to cover the sensor head. Immerse the sensor inside the ORP standard buffer solution. Wait until values are stabilized over time and type 'N' to continue.

Figure: Immersing the sensor inside the calibration buffer solution

Step 4: Save calibration data into the sensor by typing operator's name and date of calibration. Then, the sensor values will be printed on the screen to check if the measures are done correctly.

Figure: Save the calibration data

Step 5: Remove the sensor from the buffer solution and clean it carefully as described in the next section.

Cleaning the sensor

The PHEHT sensor probe needs to be cleaned periodically to remove the possible fouling or other biologic material that could appear in the sensor.

Before cleaning the sensor, please keep in mind that the crystal electrode used for pH measurement is very fragile. Use tap water, soap to rinse the sensor carefully and a soft towel to dry it and remove the biologic material. Avoid using absorbent paper because the glass electrode is extremely vulnerable to frictions. Moreover, if the ORP sensor of the PHEHT sensor probe is still dirty, use a soft and fine sandpaper to clean the metallic part.

Figure: Cleaning the sensor

The presence of biofilm in the sensor electrodes can introduce measuring errors.

On top of that, the cartridge could be replaced if it is damaged for some reason. Contact Libelium for more information.

Finally, if the sensor is not going to be used during a large period, it is important to clean the sensor prior to storing it. Remember to place the protection cap together with a moisture absorbent element (like a piece of cotton) and also to fill the cap with the storage solution for PHEHT probe. This will avoid the electrode to become deteriorated. The storage solution is sold as an accessory for the sensor.

Installation

It is important to think about a few aspects before installing the sensor on the field:

• The sensor body should be easily accessible for cleaning, regular maintenance and calibration.

• The sensor body must be firmly fastened to avoid sensor swing and possible collisions with the surrounding objects that can damage the sensor.

• If the sensor is installed totally immersed, it should be fastened from the body and not from the cable. The cable is not designed to hold the sensor and it could be damaged.

• Avoid bubbles around the sensor.

• For those users interested in measuring directly inside pipes, there are pipe segments with a protected measurement point. As an optional accessory for this sensor, Libelium offers a pipe mounting adapter (available in PVC and in stainless steel) which can be connected to those special pipe segments.

Figure: Typical installation on a pipe

Figure: Another Typical installation on a lake

If the sensor is used in a hard environment where animals, solids or other environmental elements can damage the sensor, a protection strainer is available as an accessory of extra protection. Contact our Sales department through the next link if you require more information: http://www.libelium.com/contact.

Figure: Protection strainer accessory

A complete sensor manual can be found on the manufacturer's website.

Application examples

• Industrial and public sewage treatment plants

• Wastewater management (nitrification and de-nitrification)

• Surface water monitoring

• Drinking water monitoring

Calibration report

Together with this sensor we provide a factory calibration report in which the manufacturer ensures that the sensor has passed a calibration procedure with traceability.

Conductivity, salinity and temperature C4E sensor probe

The Conductivity, salinity and temperature C4E sensor probe uses a four-electrode technology that offers great accuracy with low maintenance. For this, the electrolytes do not need to be replaced. Besides, calibration intervals are long due to the low drift of its measures.

The conductivity values are internally compensated with the temperature provided by the embedded sensor. Moreover, it does not consume oxygen and therefore does not require a minimum inflow.

Figure: Conductivity, salinity and temperature C4E sensor probe

Specifications

Conductivity sensor:

Technology: 4 electrode (2 graphite, 2 platinum) Ranges:

• 0 - 200 µS/cm

• 0 - 2 mS/cm

• 0 - 20 mS/cm

• 0 - 200 mS/cm

Resolution: 0.01 to 1 according the range Accuracy: ±1% of the full range Measurement range (salinity): 5 - 60 g/kg Measurement range (TDS - Kcl): 0 - 133 000 ppm

Temperature sensor:

Technology: NTC Range: 0 °C to +50 °C Resolution: 0.01 °C Accuracy: ±0.5 °C Response time: <5 s

Common:

Default cable length: 15 m Maximum pressure: 5 bars Body material: PVC IP classification: IP68 Storage temperature: 0 °C to +60 °C

Figure: Sensor parts: (1) temperature sensor, (2) head with 4 electrodes, (3) sensor body

Figure: Dimensions of the C4E sensor probe

Measurement process

The C4E sensor provides a digital signal using the SDI-12 protocol.

Reading code:

{
    // 1. Declare an object for the sensor
    Aqualabo_C4E mySensor(XTR_SOCKET_A);
    // 2. Turn ON the sensor
    mySensor.ON();
    // 3. Read the sensor. Values stored in class variables
    // Check complete code example for details
    mySensor.read();
    // 4. Turn off the sensor
    mySensor.OFF();
}

During the sensor measurement, there is a small stabilization time of a few seconds, so it is recommendable to wait until the values remains stable over time.

A complete example code for reading this sensor probe can be found in the following link: https://development.libelium.com/sw-xtr-15-c4e-sensor-reading

Socket

Connect the C4E sensor probe to Plug & Sense! Smart Water Xtreme in any of the sockets shown in the image below.

Figure: Available sockets for the C4E sensor probe

Maintenance

Calibration

By default, the sensor is factory-calibrated, therefore calibration may not be needed for the first usage. However, to increase the sensor accuracy if deviations are detected, calibration would be necessary. Nevertheless, before carrying out the sensor calibration, please bear in mind the next comments:

• The sensor and the buffer solutions must have the same temperature, so before starting the calibration process leave all the necessary elements in the same temperature conditions. Besides, wait for sensor temperature stabilization once it has been immersed.

• During the sensor measurement, there is a small stabilization time of a few seconds, so please wait until the values remain stable over time.

• The calibration must be done every month to get a reasonable accuracy in the measurements. However, depending on the application, the time between two calibrations would vary. It is highly recommended to do a test as close as possible to the conditions of the final application to check the sensor drift over time. This will allow adjusting the calibration periods according to the required accuracy.

• The buffer solution bottles must be closed properly after the usage, to prevent deviations on the default values.

First of all, ensure that all necessary elements are present. It is important that if a calibration process is started, it should be completed to save the results in the sensor internal memory. Do not abandon the calibration process and always follow the given steps and guidelines to avoid a sensor misconfiguration. If the process needs to be repeated or abandoned, always type the 'Q' command to exit the calibration procedure.

Libelium provides the necessary standard buffer solution to calibrate the Smart Water Xtreme sensor probes. Refer to the calibration solution section for more information.

Figure: Necessary elements for C4E sensor probe calibration

The sensor calibration can be done only on socket E. Owing to that, connect the sensor probe to socket E of the Plug & Sense! Smart Water Xtreme unit to calibrate the sensor, as shown in the image below. Do not use any other Plug & Sense! socket to calibrate a sensor. It will not work.

Figure: Connecting the sensor to the calibration socket

The C4E sensor probe allows to calibrate temperature and conductivity. Please read below the necessary steps to calibrate each parameter.

Temperature calibration

The temperature calibration process is the same for all Plug & Sense! Smart Water Xtreme sensor probes. Refer to the previously described temperature calibration section of the OPTOD sensor probe for details.

Conductivity calibration

The conductivity calibration is based in a two-point calibration process. On top of that, the user should know the expected conductivity and salinity values of the final application in order to decide which buffer solutions are the best by choosing the closest values.

There are 3 different Calibration kits for Conductivity: K=0.1, K=1; K=10. The K factor is related to the salinity of the water we want to measure. Each calibration kit takes 2 solutions:

• K=0.1

  • around 84 µS/cm

  • around 1400 µS/cm

• K=1

  • around 12000 µS/cm

  • around 80000 µS/cm

• K=10

  • around 12000 µS/cm

  • around 150000 µS/cm

The concentration value may vary in each batch with respect to the value shown above, due to the nature of the manufacturing process. That is why we wrote "around". The sticker in each bottle indicates the exact value. Please notice that the software implemented for this calibration procedure is flexible, so it is valid for any concentration values.

In the next table we see the typical conductivity depending on the kind of water we want to monitor:

Table of aqueous conductivities

Solution	μS/cm	mS/cm	ppm
Totally pure water	0.055	-	-
Typical DI water	0.1	-	-
Distilled water	0.5	-	-
Domestic "tap" water	500-800	0.5-0.8	250-400
Potable water (max)	1055	1.055	528
Sea water	50000 - 60000	56	28000

It can be seen that the relation between conductivity and dissolved solids is approximately:

2 µS/cm = 1 ppm (which is the same as 1 mg/l)

Upload the conductivity calibration example for the C4E sensor probe. The code uses the serial monitor to assist the user with messages and recommendations. The main steps are described below, but the full details are provided in the code.

Step 1: Select the desired sensor probe range according to the expected conductivity to be measured.

Step 2: Type the first calibration point (offset) on the serial monitor and press enter. Normally it is set to zero (sensor exposed to air). So keep the sensor exposed to the air and wait till measure stabilization over time. Then type 'N' to continue. Remember to remove the black protection cap.

Figure: Type the first calibration point on the serial monitor

Step 3: Type the second calibration point (slope) on the serial monitor and press enter.

Figure: Type the second calibration point on the serial monitor

Step 4: Pour enough buffer solution in a clean baker to cover the sensor head. Immerse the sensor inside the chosen conductivity standard buffer solution. Wait until values are stabilized over time and type 'N' to continue.

Figure: Immersing the sensor inside the calibration buffer solution

Step 4: Save calibration data into the sensor by typing operator's name and date of calibration. Then, the sensor values will be printed on the screen to check if the measures are done correctly.

Figure: Save the calibration data

Step 5: Remove the sensor from the buffer solution and clean it carefully as described below.

Cleaning the sensor

The C4E sensor probe needs to be cleaned periodically to remove the possible fouling or other biologic material that could appear in the sensor. The presence of biofilm in the sensor electrodes can introduce measuring errors.

Use tap water, soap to rinse the sensor carefully and a soft towel to dry it and remove the biological material. If the biofilm persists on the electrodes, use an abrasive strip through the sensor head slot to clean the electrodes under a stream of running water.

Figure: Cleaning the sensor

Finally, if the sensor is not going to be used during a large period, it is important to clean the sensor prior to storing it. Remember to place the protection cap together with a moisture absorbent element (like a piece of cotton).

Installation

It is important to think about a few aspects before installing the sensor on the field:

• The sensor body should be easily accessible for cleaning, regular maintenance and calibration.

• The sensor body must be firmly fastened to avoid sensor swing and possible collisions with the surrounding objects that can damage the sensor.

• If the sensor is installed totally immersed, it should be fastened from the body and not from the cable. The cable is not designed to hold the sensor and it could be damaged.

• Avoid bubbles around the sensor.

• For those users interested in measuring directly inside pipes, there are pipe segments with a protected measurement point. As an optional accessory for this sensor, Libelium offers a pipe mounting adapter (available in PVC and in stainless steel) that can be connected to those special pipe segments.

Figure: Typical installation on a pipe

Figure: Another Typical installation on a lake

If the sensor is used in a hard environment where animals, solids or other environmental elements can damage the sensor, a protection strainer is available as an accessory of extra protection. Contact our Sales department through the next link if you require more information: http://www.libelium.com/contact

Figure: Protection strainer accessory

A complete sensor manual can be found on the manufacturer's website.

Application examples

• Industrial and public sewage treatment plants

• Wastewater management (nitrification and de-nitrification)

• Surface water monitoring

• Drinking water monitoring

Calibration report

Together with this sensor we provide a factory calibration report in which the manufacturer ensures that the sensor has passed a calibration procedure with traceability.

Inductive conductivity, salinity and temperature CTZN sensor probe

The Inductive conductivity, salinity and temperature CTZN sensor probe has a ring-type coil to measure the conductivity. This technology allows the sensor to avoid biofilm interferences, increasing the time between calibration periods and even avoiding most of the maintenance tasks.

In addition to conductivity, the CTZN sensor probe is able to measure salinity and temperature, all included in a compact and robust probe suitable for the most typical applications.

Figure: Inductive conductivity, salinity and temperature CTZN sensor probe

Specifications

Conductivity sensor:

Technology: Inductive coil Ranges: 0 -- 100 mS/cm Resolution: 0.1 Measurement range (salinity): 5 - 60 g/kg Working temperature: 0 to 50 °C Response time: 90% of the value in less than 30 seconds

Temperature sensor:

Technology: NTC Range: 0 °C to +50 °C Resolution: 0.01 °C Accuracy: ±0.5 °C

Common:

Default cable length: 15 m Maximum pressure: 5 bars Body material: PVC IP classification: IP68 Storage temperature: -10 °C to +60 °C

Figure: Sensor parts: (1) conductivity coil, (2) temperature sensor, (3) sensor body

Figure: Dimensions of the CTZN sensor probe

Measurement process

The CTZN sensor provides a digital signal using the SDI-12 protocol.

Reading code:

{
    // 1. Declare an object for the sensor
    Aqualabo_CTZN mySensor(XTR_SOCKET_A);
    // 2. Turn ON the sensor
    mySensor.ON();
    // 3. Read the sensor. Values stored in class variables
    // Check complete code example for details
    mySensor.read();
    // 4. Turn off the sensor
    mySensor.OFF();
}

During the sensor measurement, there is a small stabilization time of a few seconds, so it is recommendable to wait until the values remain stable over time.

A complete example code for reading this sensor probe can be found in the following link: https://development.libelium.com/sw-xtr-23-ctzn-sensor-reading

Socket

Connect the CTZN sensor probe to Plug & Sense! Smart Water Xtreme in any of the sockets shown in the image below.

Figure: Available sockets for the CTZN sensor probe

Maintenance

Calibration

By default, the sensor is factory-calibrated, therefore calibration may not be needed for the first usage. However, to increase the sensor accuracy if deviations are detected, calibration would be necessary. Nevertheless, before carrying out the sensor calibration, please bear in mind the next comments:

• The sensor and the buffer solutions must have the same temperature, so before starting the calibration process leave all the necessary elements in the same temperature conditions. Besides, wait for sensor temperature stabilization once it has been immersed.

• During the sensor measurement, there is a small stabilization time of a few seconds, so please wait until the values remain stable over time.

• The calibration must be done every 2 months to get a reasonable accuracy in the measurements. However, depending on the application, the time between two calibrations would vary. It is highly recommended to do a test as close as possible to the conditions of the final application to check the sensor drift over time. This will allow adjusting the calibration periods according to the required accuracy.

• The buffer solution bottles must be closed properly after usage, to prevent deviations on the default values.

First of all, ensure that all necessary elements are present. It is important that if a calibration process is started, it should be completed to save the results in the sensor internal memory. Do not abandon the calibration process and always follow the given steps and guidelines to avoid a sensor misconfiguration. If the process needs to be repeated or abandoned, always type the 'Q' command to exit the calibration procedure.

Libelium provides the necessary standard buffer solution to calibrate the Smart Water Xtreme sensor probes. Refer to the calibration solution section for more information.

Figure: Necessary elements for CTZN sensor probe calibration

The sensor calibration can be done only on socket E. Owing to that, connect the sensor probe to socket E of the Plug & Sense! Smart Water Xtreme unit to calibrate the sensor, as shown in the image below. Do not use any other Plug & Sense! socket to calibrate a sensor. It will not work.

Figure: Connecting the sensor to the calibration socket

The CTZN sensor probe allows to calibrate temperature and conductivity. Please read below the necessary steps to calibrate each parameter.

Temperature calibration

The temperature calibration process is the same for all Plug & Sense! Smart Water Xtreme sensor probes. Refer to the previously described temperature calibration section of the OPTOD sensor probe for details.

Conductivity calibration

The conductivity calibration is based on a two-point calibration process. On top of that, the user should know the expected conductivity and salinity values of the final application in order to decide which buffer solutions are the best by choosing the closest values.

There are 3 different Calibration kits for Conductivity: K=0.1, K=1; K=10. The K factor is related to the salinity of the water we want to measure. Each calibration kit takes 2 solutions:

• K=0.1

  • around 84 µS/cm

  • around 1400 µS/cm

• K=1

  • around 12000 µS/cm

  • around 80000 µS/cm

• K=10

  • around 12000 µS/cm

  • around 150000 µS/cm

The concentration value may vary in each batch with respect to the value shown above, due to the nature of the manufacturing process. That is why we wrote "around". The sticker in each bottle indicates the exact value. Please notice that the software implemented for this calibration procedure is flexible, so it is valid for any concentration values.

In the next table we see the typical conductivity depending on the kind of water we want to monitor:

Table of aqueous conductivities

Solution	µS/cm	mS/cm	ppm
Totally pure water	0.055	-	-
Typical DI water	0.1	-	-
Distilled water	0.5	-	-
Domestic "tap" water	500-800	0.5-0.8	250-400
Potable water (max)	1055	1.055	528
Sea water	50000 - 60000	56	28000

It can be seen that the relation between conductivity and dissolved solids is approximately:

2 µS/cm = 1 ppm (which is the same as 1 mg/l)

Upload the conductivity calibration example for the CTZN sensor probe. The code uses the serial monitor to assist the user with messages and recommendations. The main steps are described below, but the full details are provided in the code.

Step 1: Type the first calibration point (offset) on the serial monitor and press enter. Normally it is set to zero (sensor exposed to air). So keep the sensor exposed to the air and wait till measure stabilization over time. Then type 'N' to continue. Remember to remove the black protection cap.

Figure: Type the first calibration point on the serial monitor

Do not discard the black protection cap and keep it for the future. It will be useful if the sensor needs to be stored for a large period.

Step 2: Type the second calibration point (slope) on the serial monitor and press enter.

Figure: Type the second calibration point on the serial monitor

Step 3: Pour enough buffer solution in a clean baker to cover the sensor head. Immerse the sensor inside the chosen conductivity standard buffer solution. Wait until values are stabilized over time and type 'N' to continue.

Figure: Immersing the sensor inside the calibration buffer solution

Step 4: Save calibration data into the sensor by typing operators name and date of calibration. Then, the sensor values will be printed on the screen to check if the measures are done correctly.

Figure: Save the calibration data

Step 5: Remove the sensor from the buffer solution and clean it carefully as described below.

Cleaning the sensor

The CTZN sensor probe is designed to avoid periodic cleaning due to its immunity to fouling effects.

However, depending the environment it is recommendable to check the sensor to avoid solids to get tangled up into the sensor coil.

Finally, if the sensor is not going to be used during a large period, it is important to clean the sensor prior to storing it. Use tap water, soap to rinse the sensor carefully and a soft towel to dry it and remove the biologic material.

Figure: Cleaning the sensor

Installation

It is important to think about a few aspects before installing the sensor on the field:

• The sensor body should be easily accessible for cleaning, regular maintenance and calibration.

• The sensor body must be firmly fastened to avoid sensor swing and possible collisions with the surrounding objects that can damage the sensor.

• If the sensor is installed totally immersed., it should be fastened from the body and not from the cable. The cable is not designed to hold the sensor and it could be damaged.

• Avoid bubbles around the sensor.

• For those users interested in measuring directly inside pipes, there are pipe segments with a protected measurement point. As an optional accessory for this sensor, Libelium offers a pipe mounting adapter (available in PVC and in stainless steel) which can be connected to those special pipe segments.

Figure: Typical installation on a pipe

Figure: Another Typical installation on a lake

A complete sensor manual can be found on the manufacturer's website.

Application examples

• Urban wastewater treatment

• Industrial effluent treatment

• Surface water monitoring

• Sea water

• Fish farming

Calibration report

Together with this sensor we provide a factory calibration report in which the manufacturer ensures that the sensor has passed a calibration procedure with traceability.

Turbidity and temperature NTU sensor probe

The Turbidity and temperature NTU sensor probe is based in infrared light reflections which allows measuring turbidity in a great range of applications. Besides, the sensor measures suspended solids and also an internal temperature sensor is included for temperature compensation of the turbidity measures.

Some sensors in the market calculate the suspended solids from the turbidity value. By contrast, the NTU sensor probe takes its own measure. However, to measure suspended solids correctly, the NTU sensor probe is directly calibrated on the material to be measured and an external laboratory is needed to analyze the sample. This service is not provided by Libelium.

The NTU sensor probe measures according to DIN EN ISO 7027, required in many Smart Water quality applications.

Note: The optical windows of the NTU sensor probe is vulnerable to chemicals (organic solvents, acids and strong bases, peroxide and hydrocarbons). Avoid using the sensor if they are present in your application.

Figure: Turbidity and temperature NTU sensor probe

Specifications

Turbidity sensor:

Technology: Optical infrared (IR 880 nm) Ranges NTU: 0 to 4000 NTU in 5 ranges:

• 0 - 50 NTU

• 0 - 200 NTU

• 0 - 1000 NTU

• 0 - 4000 NTU

• AUTOMATIC

Ranges mg/L: 0 to 4500 mg/L

• Range 0 - 500 mg/L according to NF EN 872

• Range >500 mg/L according to NF T 90 105 2

Resolution: 0.01 to 1 NTU - mg/L Accuracy: <5% of the reading Response time: <5 s

Temperature sensor:

Technology: NTC Range: 0 °C to +50 °C Resolution: 0.01 °C Accuracy: ±0.5 °C

Common:

Default cable length: 15 m Maximum pressure: 5 bars Body material: DELRIN IP classification: IP68 Storage temperature: 0 °C to +60 °C

Figure: Sensor parts: (1) temperature sensor, (2) optical window, (3) sensor body

Figure: Dimensions of the NTU sensor probe

Measurement process

The sensor probe provides a digital signal using the SDI-12 protocol.

Reading code:

{
    // 1. Declare an object for the sensor
    Aqualabo_NTU mySensor(XTR_SOCKET_A);
    // 2. Turn ON the sensor
    mySensor.ON();
    // 3. Read the sensor. Values stored in class variables
    // Check complete code example for details
    mySensor.read();
    // 4. Turn off the sensor
    mySensor.OFF();
}

During the sensor measurement, there is a small stabilization time of a few seconds, so it is recommendable to wait until the values remain stable over time.

A complete example code for reading this sensor probe can be found in the following link: https://development.libelium.com/sw-xtr-19-ntu-sensor-reading

Socket

Connect the NTU sensor probe to Plug & Sense! Smart Water Xtreme in any of the sockets shown in the image below.

Figure: Available sockets for the NTU sensor probe

Maintenance

Calibration

By default, the sensor is factory-calibrated, therefore calibration may not be needed for the first usage. However, to increase the sensor accuracy if deviations are detected, calibration would be necessary. Nevertheless, before carrying out the sensor calibration, please bear in mind the next comments:

• The sensor and the buffer solutions must have the same temperature, so before starting the calibration process leave all the necessary elements in the same temperature conditions. Besides, wait for sensor temperature stabilization once it has been immersed.

• During the sensor measurement, there is a small stabilization time of a few seconds, so please wait until the values remain stable over time.

• The calibration must be done every month to get a reasonable accuracy in the measurements. However, depending on the application, the time between two calibrations would vary. It is highly recommended to do a test as close as possible to the conditions of the final application to check the sensor drift over time. This will allow adjusting the calibration periods according to the required accuracy.

• The buffer solution bottles must be closed properly after usage, to prevent deviations on the default values.

First of all, ensure that all necessary elements are present. It is important that if a calibration process is started, it should be completed to save the results in the sensor internal memory. Do not abandon the calibration process and always follow the given steps and guidelines to avoid a sensor misconfiguration. If the process needs to be repeated or abandoned, always type the 'Q' command to exit the calibration procedure.

Libelium provides the necessary standard buffer solution to calibrate the Smart Water Xtreme sensor probes. Refer to the calibration solution section for more information.

Figure: Necessary elements for NTU sensor probe calibration

The sensor calibration can be done only on socket E. Owing to that, connect the sensor probe to socket E of the Plug & Sense! Smart Water Xtreme unit to calibrate the sensor, as shown in the image below. Do not use any other Plug & Sense! socket to calibrate a sensor. It will not work.

Figure: Connecting the sensor to the calibration socket

The NTU sensor probe allows to calibrate temperature and turbidity. Please read below the necessary steps to calibrate each parameter.

Temperature calibration

The temperature calibration process is the same for all Plug & Sense! Smart Water Xtreme sensor probes. Refer to the previously described temperature calibration section of the OPTOD sensor probe for details.

NTU calibration

By default the NTU sensor is in automatic range, which means that the internal circuitry is able to select the best sensor range according to the measure which is taking place. If turbidity values are between two ranges, some variations may be observed as a result of the automatic mode where the sensor is trying to adjust itself.

The turbidity calibration requires a formazine solution with a concentration matching the middle of the

selected range. The solution could be prepared from a 4000 NTU standard solution mixing the necessary parts with distilled water.

The solutions of concentrations lower than 1000 NTU deteriorate fast, so do not preserve a solution for several days. By contrast, solutions around 2000 NTU could be preserved in the refrigerator for 2 or 3 weeks in an opaque and properly closed flask. Remember to shake the solutions before using them.

One instance could be selecting the range of 0 to 1000 NTU. it would be needed a concentration of 500 NTU as a second calibration point (half range). As an example, a reasonable amount of liquid to calibrate would be 200 ml, therefore to obtain 200 ml with a concentration of 500 NTU it would be needed 25 ml of 4000 NTU solution and 175 ml of distilled water (up to 200 ml).

Step 1: Select the range of the sensor to calibrate.

Step 2: Type the first calibration point (offset) on the serial monitor and press enter.

Figure: Type the first calibration point on the serial monitor

Step 3: The first calibration point (offset) is intended to be zero. So immerse the sensor in distilled water. The sensor needs to be at least 5 cm far from the baker walls to avoid side effects that could distort the measurement. Remove the black protection cap before immersing the sensor in the buffer solution. Wait until values are stabilized over time and type 'N' to continue.

Do not discard the black protection cap and keep it for the future. It will be useful if the sensor needs to be stored for a large period.

Figure: Immersing the sensor inside the calibration buffer solution

Step 4: Remove the sensor from the buffer solution and clean it carefully as previously described.

Step 5: Type the second calibration point (slope) on the serial monitor and press enter.

Figure: Type the second calibration point on the serial monitor

Step 6: Pour enough buffer solution in a clean baker to cover the sensor head. Immerse the sensor inside the desired buffer solution for the selected range. Wait until values are stabilized over time, but maintaining the solution under agitation. Type 'N' to continue.

Step 7: Save calibration data into the sensor by typing operator's name and date of calibration. Then, the sensor values will be printed on the screen to check if the measures are done correctly.

Figure: Save the calibration data

Cleaning the sensor

The NTU sensor probe needs to be cleaned periodically to remove the possible fouling or other biologic material that could appear in the sensor. Organic deposits present on the sensor lens, such as a biofilm or silt, may cause measurement errors. These deposits should be removed carefully with warm soapy water and a soft sponge. Never use abrasive agents (e.g. scouring sponge). In addition, calcium deposits could be removed by immersing the sensor in a diluted hydrochloric acid solution (maximum concentration of 5%) for several minutes.

Figure: Cleaning the sensor

Finally, if the sensor is not going to be used during a large period, it is important to clean the sensor prior to storing it. Remember to place the protection cap together with a moisture absorbent element (like a piece of cotton).

Installation

It is important to think about a few aspects before installing the sensor on the field:

• The sensor body should be easily accessible for cleaning, regular maintenance and calibration.

• The sensor body must be firmly fastened to avoid sensor swing and possible collisions with the surrounding objects that can damage the sensor.

• If the sensor is installed totally immersed, it should be fastened from the body and not from the cable. The cable is not designed to hold the sensor and it could be damaged.

• Avoid bubbles around the sensor.

• For those users interested in measuring directly inside pipes, there are pipe segments with a protected measurement point. As an optional accessory for this sensor, Libelium offers a pipe mounting adapter (available in PVC and in stainless steel) that can be connected to those special pipe segments.

Figure: Typical installation on a pipe

Figure: Another Typical installation on a lake

Moreover, due to the optical sensor technology, the NTU sensor probe is affected by external light sources that could distort the measures. Try to place the sensor where light does not reach the sensor probe's head.

Figure: Turbidity sensor probe wrongly and correctly placed

If the sensor is used in a hard environment where animals, solids or other environmental elements can damage the sensor, a protection strainer is available as an accessory of extra protection. Contact our Sales department through the next link if you require more information: http://www.libelium.com/contact.

Figure: Protection strainer accessory

A complete sensor manual can be found on the manufacturer's website.

Application examples

• Drinking water management

• Fish farming

• Industrial and public sewage treatment plants

• Process engineering plants

Calibration report

Together with this sensor we provide a factory calibration report in which the manufacturer ensures that the sensor has passed a calibration procedure with traceability.

Suspended solids, turbidity, sludge blanket and temperature MES5 sensor probe

The Suspended solids, turbidity, sludge blanket and temperature MES5 sensor probe gives 4 different parameters in a single probe. It is based on the attenuation of an infrared signal through an optical path in the probe's head. The given measures are temperature compensated to increase the accuracy.

However, to measure suspended solids, the MES5 sensor probe is directly calibrated on the material to be measured (sample of sludge) and an external laboratory is needed to analyze the sample. This service is not provided by Libelium.

Figure: Suspended solids, turbidity, sludge blanket and temperature MES5 sensor probe

Specifications

Turbidity sensor:

Technology: Optical infrared (IR 870 nm) Ranges:

• SS : 0 - 50 g/L

• Turbidity : 0 - 4000 FAU

• Sludge blanket : 0 - 100%

Resolution:

• SS : 0.01 g/L

• Turbidity : 0.01 to 1 FAU

• Sludge blanket : 0.01 to 0.1%

Accuracy:

• SS <10%

• Turbidity : ±5% (range 200 - 4000 FAU)

• Sludge blanket : ±2%

Response time: < 35 seconds

Temperature sensor:

Technology: NTC Range: -5 °C to +50 °C Resolution: 0.01 °C Accuracy: ±0.5 °C

Common:

Default cable length: 15 m IP classification: IP68 Maximum pressure: 5 bars Body material: DELRIN Storage temperature: 0 °C to +60 °C

Figure: Sensor parts: (1) optical window, (2) temperature sensor, (3) sensor body

Figure: Dimensions of the MES5 sensor probe

Measurement process

The MES5 sensor provides a digital signal using the SDI-12 protocol.

Reading code:

{
    // 1. Declare an object for the sensor
    Aqualabo_MES5 mySensor(XTR_SOCKET_A);
    // 2. Turn ON the sensor
    mySensor.ON();
    // 3. Read the sensor. Values stored in class variables
    // Check complete code example for details
    mySensor.read();
    // 4. Turn off the sensor
    mySensor.OFF();
}

During the sensor measurement, there is a small stabilization time of a few seconds, so it is recommendable to wait until the values remain stable over time.

A complete example code for reading this sensor probe can be found in the following link: https://development.libelium.com/sw-xtr-27-mes5-sensor-reading

Socket

Connect the MES5 sensor probe to Plug & Sense! Smart Water Xtreme in any of the sockets shown in the image below.

Figure: Available sockets for the MES5 sensor probe

Maintenance

Calibration

By default, the sensor is factory-calibrated, therefore calibration may not be needed for the first usage. However, to increase the sensor accuracy if deviations are detected, calibration would be necessary. Nevertheless, before carrying out the sensor calibration, please bear in mind the next comments:

• The sensor and the buffer solutions must have the same temperature, so before starting the calibration process leave all the necessary elements in the same temperature conditions. Besides, wait for sensor temperature stabilization once it has been immersed.

• During the sensor measurement, there is a small stabilization time of a few seconds, so please wait until the values remain stable over time.

• The calibration must be done every month to get a reasonable accuracy in the measurements. However, depending on the application, the time between two calibrations would vary. It is highly recommended to do a test as close as possible to the conditions of the final application to check the sensor drift over time. This will allow adjusting the calibration periods according to the required accuracy.

• The buffer solution bottles must be closed properly after usage, to prevent deviations on the default values.

• The sensor needs to be rinsed with clean water before each calibration.

First of all, ensure that all necessary elements are present. It is important that if a calibration process is started, it should be completed to save the results in the sensor internal memory. Do not abandon the calibration process and always follow the given steps and guidelines to avoid a sensor misconfiguration. If the process needs to be repeated or abandoned, always type the 'Q' command to exit the calibration procedure.

Libelium provides the necessary standard buffer solution to calibrate the Smart Water Xtreme sensor probes. Refer to the calibration solution section for more information.

Figure: Necessary elements for MES5 sensor probe calibration

The sensor calibration can be done only on socket E. Owing to that, connect the sensor probe to socket E of the Plug & Sense! Smart Water Xtreme unit to calibrate the sensor, as shown in the image below. Do not use any other Plug & Sense! socket to calibrate a sensor. It will not work.

Figure: Connecting the sensor to the calibration socket

The MES5 sensor probe does not allow to calibrate suspended solids by itself and an external laboratory is needed to analyze the sample of the sludge blanket. This service is not provided by Libelium.

However, it allows calibrating temperature and turbidity. Please read below the necessary steps to calibrate each parameter.

Temperature calibration

The temperature calibration process is the same for all Plug & Sense! Smart Water Xtreme sensor probes. Refer to the previously described temperature calibration section of the OPTOD sensor probe for details.

Turbidity calibration

The turbidity calibration process is the same for the MES5 and NTU sensor probes (with the exception that the MES5 sensor probe only has one range). Refer to the previously described turbidity calibration section of NTU sensor probe for details.

Cleaning the sensor

The MES5 sensor probe needs to be cleaned periodically to remove the possible fouling or other biologic material that could appear in the sensor. Organic deposits present on the sensor lens, such as a biofilm or silt, may cause measurement errors. These deposits should be removed carefully with warm soapy water and a soft sponge. Never use abrasive agents (e.g. scouring sponge). In addition, calcium deposits can be removed by immersing the sensor in a diluted hydrochloric acid solution (concentration max. 5%) for several minutes.

Figure: Cleaning the sensor

Finally, if the sensor is not going to be used during a large period, it is important to clean the sensor prior to storing it. Remember to place the protection cap together with a moisture absorbent element (like a piece of cotton).

Installation

It is important to think about a few aspects before installing the sensor on the field:

• The sensor body should be easily accessible for cleaning, regular maintenance and calibration.

• The sensor body must be firmly fastened to avoid sensor swing and possible collisions with the surrounding objects that can damage the sensor.

• If the sensor is installed totally immersed, it should be fastened from the body and not from the cable. The cable is not designed to hold the sensor and it could be damaged.

• Avoid bubbles around the sensor.

• For those users interested in measuring directly inside pipes, there are pipe segments with a protected measurement point. As an optional accessory for this sensor, Libelium offers a pipe mounting adapter (available in PVC and in stainless steel) that can be connected to those special pipe segments.

Figure: Typical installation on a pipe

Figure: Another Typical installation on a lake

A complete sensor manual can be found on the manufacturer's website.

Application examples

• Urban Waste water treatment (Inlet/sewage water (SS, Turbidity), Aeration basin (SS), Outlet (Turbidity)

• Treatment of industrial effluents (Aeration basin (SS)), Clarifier (Sludge blanket), Outlet (Turbidity)

• Sludge treatment (Centrifugation)

• Dredging site (turbidity)

Calibration report

Together with this sensor we provide a factory calibration report in which the manufacturer ensures that the sensor has passed a calibration procedure with traceability.

Temperature, humidity and pressure sensor probe (Bosch BME280)

The Bosch BME280 includes a humidity sensor that features an extremely fast response time which supports performance requirements for emerging applications such as context awareness, and high accuracy over a wide temperature range. The pressure sensor is an absolute barometric pressure sensor with features exceptionally high accuracy and resolution at very low noise. The integrated temperature sensor has been optimized for very low noise and high resolution. It is primarily used for temperature compensation of the pressure and humidity sensors, and can also be used for estimating ambient temperature.

Figure: Temperature, humidity and pressure sensor probe (Bosch BME280)

Specifications

Temperature sensor:

Operational range: -40 ~ +85 ºC Full accuracy range: 0 ~ +65 ºC Accuracy: ±1 ºC (range 0 ºC ~ +65 ºC) Response time: 1.65 seconds (63% response from +30 to +125 °C)

Humidity sensor:

Measurement range: 0 ~ 100% of relative humidity (for temperatures < 0 °C and > 60 °C see figure below) Accuracy: < ±3% RH (at 25 ºC, range 20 ~ 80%) Hysteresis: ±1% RH Operating temperature: -40 ~ +85 ºC Response time (63% of step 90% to 0% or 0% to 90%): 1 second

Figure: Humidity sensor operating range

Pressure sensor:

Measurement range: 30 ~ 110 kPa Operational temperature range: -40 ~ +85 ºC Full accuracy temperature range: 0 ~ +65 ºC Absolute accuracy: ±0.1 kPa (0 ~ 65 ºC)

Measurement process

The Temperature, humidity and pressure sensor provides a digital signal using the I2C protocol.

Reading code:

{
    // 1. Declare an object for the sensor
    bme mySensor(XTR_SOCKET_A);
    // 2. Turn ON the sensor
    mySensor.ON();
    // 3. Read the sensor. Store parameters in local variables
    float temperature = mySensor.getTemperature();
    float humidity = mySensor.getHumidity();
    float pressure = mySensor.getPressure();
    // 4. Turn off the sensor
    mySensor.OFF();
}

You can find a complete example code for reading this sensor probe in the following link: https://development.libelium.com/sw-xtr-32-bme280-sensor-reading

Socket

Connect the Temperature, humidity and pressure sensor probe (Bosch BME280) to Plug & Sense! Smart Water Xtreme in the sockets A or D.

Application examples

• Weather observation and forecast

• Evapotranspiration analysis

• Control heating, ventilation or air conditioning in greenhouses

• Warning regarding dryness or high temperatures

• Pressure compensation for dissolved oxygen accurate calculations

Luminosity sensor probe (AMS TSL2561)

This is a light-to-digital converter that transforms light intensity into a digital signal output. This device combines one broadband photo-diode (visible plus infrared) and one infrared-responding photo-diode on a single CMOS integrated circuit capable of providing a near-photopic response over an effective 20-bit dynamic range (16-bit resolution). Two integrating ADCs convert the photo-diode currents to a digital output that represents the irradiance measured on each channel. This digital output in lux is derived using an empirical formula to approximate the human eye response.

Figure: Luminosity sensor probe (AMS TSL2561)

Specifications

Operating temperature: -30 ºC to +80 ºC Dynamic range: 0.1 to 40000 Lux Spectral range: 300 -- 1100 nm Usage: indoors and outdoors

Figure: Luminosity sensor graphic

Measurement process

The luminosity sensor provides a digital signal using the I2C protocol.

Reading code:

{
    // 1. Declare an object for the sensor
    luxes mySensor(XTR_SOCKET_A);
    // 2. Turn ON the sensor
    mySensor.ON();
    // 3. Read the sensor. Store parameters in local variables
    uint32_t luminosity = mySensor.getLuminosity();
    // 4. Turn off the sensor
    mySensor.OFF();
}

You can find a complete example code for reading this sensor probe in the following link: https://development.libelium.com/sw-xtr-33-tsl2561-sensor-reading

Socket

Connect the Luminosity sensor probe to Plug & Sense! Smart Water Xtreme in the sockets A or D.

Figure: Available sockets for the Luminosity sensor probe

Application examples

• Light presence detection

Ultrasound sensor probe (MaxBotix MB7040)

The Ultrasound sensor probe (MaxBotix MB7040) has high acoustic power output along with real-time auto calibration for changing conditions (voltage and acoustic or electrical noise) that ensure users receive the most reliable ranging data for every reading taken in air.

Figure: Ultrasound sensor (MaxBotix MB7040)

Specifications

Operation frequency: 42 kHz Maximum detection distance: 765 cm Usage: indoors and outdoors (IP-67)

Figure: Ultrasound sensor dimensions

A	1.72” dia	43.8 mm dia
B	2.00”	50.7 mm
C	0.58”	14.4 mm
D	0.31”	7.9 mm
E	0.18”	4.6 mm
F	0.1”	2.54 mm
G	3/4” National Pipe Thread Straight	3/4” National Pipe Thread Straight
H	1.032” dia	26.2 dia
i	1.37”	34.8 mm

weight: 1.76 oz. ; 50 grams

Measurement process

The ultrasound sensor provides a digital signal using the I2C protocol.

Reading code:

{
    // 1. Declare an object for the sensor
    ultrasound mySensor(XTR_SOCKET_A);
    // 2. Turn ON the sensor
    mySensor.ON();
    // 3. Read the sensor. Store parameters in local variables
    uint16_t distance = mySensor.getDistance();
    // 4. Turn off the sensor
    mySensor.OFF();
}

You can find a complete example code for reading this sensor probe in the following link: https://development.libelium.com/sw-xtr-34-mb7040-sensor-reading

Socket

Connect the Ultrasound sensor probe to Plug & Sense! Smart Water Xtreme in the sockets A or D.

Figure: Available sockets for the Ultrasound sensor probe

Installation

The ultrasound sensor probe may be placed in different positions. The sensor can be focused directly to the point we want to measure.

Figure: Ultrasound sensor (MaxBotix MB7040) installation

Application examples

• Tank level measurement

• River height control

• Early flood detection

• Sea tide monitoring

• Proximity zone detection

• People detection

• Distance measuring

• Security systems

• Motion detection

• Collision avoidance

Eureka Manta multi sensor probe

The Eureka Manta sensor probe is designed to unify a large number of sensors in only one probe. Owing to that, the Eureka Manta multi probe is highly configurable, offering a great number of parameter combinations to meet the requirements even for the most demanding applications.

Parameters like chlorophyll, Blue-Green Algae (BGA, also known as cyanobacteria), organic matter (CDOM and FDOM), ammonium, nitrates, chloride, sodium or calcium can be measured with this multi probe, achieving up to 13 different measures.

Eureka offers many accessories and combinations. The item that Libelium distributes as base includes:

• pH/ORP sensor (double)

• turbidity sensor (with an automatic wiper)

• dissolved oxygen sensor

• conductivity sensor

• temperature sensor.

Other sensors (ions, BGA, Organic Matter, etc) are available as accessories.

Ion Selective Electrode probes are not recommended for seawater applications due to their special calibration requirements and their reliability in terms of stability and accuracy. Same happens with any ISE sensor in the market. Contact your sales agent for more information.

Eureka Manta multi sensor probe is not included in the Programming Cloud Service by default. Please ask your sales agent for more information about the posibilities.

Figure: Eureka Manta multi sensor probe

Common specifications

Temperature:

Range: -5 to 50ºC Resolution: 0.01 Accuracy: 0.1

pH/ORP sensor:

pH parameter:

Range: 0 to 14 units Resolution: 0.01 Accuracy: 0.1 within 10ºC of calibration, 0.2 otherwise

ORP parameter:

Range: -999 to 999 mV Resolution: 1 Accuracy: 20 mV

Turbidity sensor:

Turbidity parameter:

Range 1: 0 to 40 FNU with accuracy 2% of reading or 0.2 Range 2: 40-400 FNU with accuracy 2% of reading or 0.2 Range 3: 400-5000 FNU with accuracy 2% of range Resolution: 4 digits with maximum of two decimals

Transmissivity parameter:

Range: 0 to 100% transmission Resolution: 4 digits Accuracy: linearity of 0.99R^2^

Dissolved oxygen (DO) sensor:

Concentration parameter:

Range 1: 0 to 20 mg/l with resolution 0.01 and accuracy 0.1 Range 2: 20 to 30 mg/l with resolution 0.01 and accuracy 0.15 Range 3: 30 to 50 mg/l with resolution 0.1 and accuracy 5% Resolution: 4 digits with maximum of two decimals

Percentage saturation parameter:

Range: 0 to 500% saturation Resolution: 0.1% Accuracy: ± 1% of range 0 -- 225 and ± 5% of range 225-500

Conductivity sensor:

Specific conductance parameter:

Range 1: 0 to 5000 μS/cm with accuracy ±0.5% of reading ±0 Range 2: 0 to 10 mS/cm with accuracy ±1% of reading ±0.001 Range 3: 10 to 100 mS/cm with accuracy 1% of reading ; 0.5% available Range 4: 100 to 275 mS/cm with accuracy 2% of reading ; 0.5% available Resolution: 4 digits with maximum of one decimal

Salinity parameter:

Range: 0 to 70 PSS Resolution: 0.01 Accuracy: 0.2

Total dissolved solids (TDS) parameter:

Range: 0 to 65 g/l Resolution: 0.1 Accuracy: 5% of reading

Specifications for accessories

Depth parameter:

Range: 0 to 10 m, vented depth (stage), 0 to 25 m depth absolute and 25 to 200 m, depth absolute. Resolution: 0.01 depth, 0.001 vented depth Accuracy: ±0.003, vented depth (stage), ±0.05, 0 – 25 m depth, ±0.4, 0 – 200 m depth

Fluorometers:

Chlorophyll a -- blue: 0 to 500 g/l Chlorophyll a -- red: > 500 g/l CDOM/FDOM: 0 to 1250 or 0 to 5000 ppb Resolution: 6 digits with maximum of two decimals Accuracy: linearity of 0.99 R²

Ion selective electrodes (ISE):

Ammonium: 0 to 100 mg/l as nitrogen Nitrate: 0 to 100 mg/l as nitrogen Chloride: 0 to 18000 mg/l Sodium: 0 to 20000 mg/l Calcium: 0 to 40000 mg/l Resolution: 0.1 Accuracy: 5% or 2 mg/l Ammonium and nitrate require tip replacement every 3 - 6 months

Common:

Diameter: 3.5" or 4" Length: 19" Temperature Range: -5 °C to +50 °C Depth rating: 200 m, maximum for ISE and TDG sensor is 15 meters IP classification: IP68 (complete and continuous immersion in water, up to 200 meters depth)

Figure: Probes assembled on the Eureka Manta multi probe

Temperature

The temperature has a range of -5 to 50ºC. This sensor never needs calibration. An optional 0.05 resolution sensor is also available.

pH/ORP

The range of pH sensor is 0 to 14 units and the range of ORP sensor is -999 to 999 mV.

pH sensor includes a refillable reference electrode, and the measure is corrected for temperature.

Platinum ORP sensor is combined with pH sensor

Turbidity

The range of this sensor is 0 to 5000 FNU in the total range.

This sensor is compensated for temperature and itered for non-turbidity spikes. It includes wiper to clean the optics.

Dissolved oxygen (DO)

This is an optical sensor (luminescence method) able to measure the concentration of dissolved oxygen and the saturation percentage in water.

The range of this sensor is 0 to 50 mg/l or 0 to 500% in saturation. The measures of this sensor are compensated for temperature and salinity.

Conductivity

This sensor is able to measure specific conductance, salinity and total dissolved solids (TDS).

The specific conductance is compensated for temperature. It includes four easy-to-clean graphite electrodes and an optional sensor provides ±0.5% of reading accuracy to 100 mS/cm.

The salinity is calculated from specific conductance. PSS = Practical Salinity Scale which is roughly equivalent to ppt.

Total dissolved solids (TDS) are calculated from specific conductance.

Depth

Depth refers to the measurement of distance beneath the water surface. Stage, which shares a similar concept, involves sensors that offer heightened precision over a narrower span (typically up to 10 meters). Unlike depth sensors, stage sensors are exposed to the atmosphere at the water's surface. The word "level" is frequently used interchangeably with stage in this context.

Depth rating is 200 meters, but maximum depth for ISE and TGD sensors is 15 meters.

Depth and stage sensors come pre-calibrated for their sensitivity to slopes, yet there are instances when recalibration is necessary to adjust their zero settings. This recalibration involves aligning the sensor to a zero reading in an air environment, preferably at the specific location where measurements are intended to be conducted.

Fluorometer Chlorophyll

Fluorometric sensors emit light at a certain wavelength and look for a very specific wavelength in return. The magnitude of the return light is relatable to the amount of the analyzed parameter. They require non-trivial calibration.

In the case of chlorophyll, two fluorometers are available with the ranges shown below:

Chlorophyll a -- blue: 0 to 500 g/l Chlorophyll a -- red: > 500 g/l

Fluorometer Phycocyanin (freshwater BGA)

Phycocyanin fluorometer works in the same way as chlorophyll fluorometer. The main applications are lakes, rivers, ground water, oceanographic, process waters, waste waters or laboratory research. The range of this fluorometer is 0 to 40,000 ppb.

Fluorometer Phycoerythrin (marine BGA)

There is a specific version of the fluorometer BGA for sea water applications with a range of 0 to 750 ppb.

Fluorometer CDOM / FDOM

The CDOM (Colored Dissolved Organic Matter) and the FDOM (Fluorescent Dissolved Organic Matter) fluorometers work in the same way as previous fluorometers.

The ranges for these fluorometers are:

CDOM: 0 to 1250 ppb FDOM: 0 to 5000 ppb

Rhodamine

The Rhodamine sensor works in the same way as previous fluorometers. The range of this sensor is 0 to 1000 ppb.

Crude Oil

The Crude Oil sensor has a range of 0 to 1500 ppb.

Refined Oil

The Refined Oil sensor has a range of 0 to 1000 ppb.

Fluorescein

The fluorescein sensor has a range of 0 to 500 ppb.

Tryptophan

The tryptophan sensor has a range of 0 to 20000 ppb.

Optical Brighteners

The optical brigteners sensor has a range of 0 to 15000 ppb.

Ion selective electrode -- Ammonium

This sensor has a membrane that is selective for ammonium. The electrode's filling solution contains a salt sensitive to ammonium, and the difference between that salt's concentration and the ammonium concentration in the measured water produces a charge separation. That charge separation is measured, relative to the reference electrode, as a voltage that changes predictably with changes in the ammonium concentration in the water adjacent the membrane.

The range of this sensor is 0 to 100 mg/l as nitrogen.

Ion selective electrode -- Nitrate

This sensor has a membrane that is selective for nitrate and works in the same way as Ammonium electrode.

The range of this sensor is 0 to 100 mg/l as nitrogen.

Ion selective electrode -- Chloride

This sensor has a membrane that is selective for chloride and works in the same way as Ammonium electrode.

The range of this sensor is 0 to 18000 mg/l.

Ion selective electrode -- Sodium

This sensor has a membrane that is selective for sodium and works in the same way as Ammonium electrode.

The range of this sensor is 0 to 20000 mg/l.

Ion selective electrode -- Calcium

This sensor has a membrane that is selective for calcium and works in the same way as Ammonium electrode.

The range of this sensor is 0 to 40000 mg/l.

Ion selective electrode -- Bromide

This sensor has a membrane that is selective for bromide and works in the same way as Ammonium electrode.

The range of this sensor is 0 to 40000 mg/l.

Total Dissolved Gas (TGD)

This sensor is compensated for temperature and the maximum depth 15m

The range of this sensor is 400 to 1,400 mm Hg.

Sensor configuration

The Eureka Manta sensor probe allows multiple configurations following the next 2 distributions. Contact your Sales agent for more information about the possibilities of this sensor.

Figure: Eureka Manta multi sensor probe configuration.

Measurement process

The Eureka sensor provides a digital signal using the RS-232 protocol.

Reading code:

{
    // 1. Declare an object for the sensor
    eureka mySensor;
    // 2. Turn ON the sensor
    mySensor.ON();
    // 3. Read the sensor. Values stored in class variables
    // Check complete code example for details
    mySensor.read();
    // 4. Turn off the sensor
    mySensor.OFF();
}

During the sensor measurement, there is a small stabilization time of a few seconds, so it is recommendable to wait until the values remains stable over time.

A complete example code for reading this sensor probe can be found in the development section of Libelium website.

Socket

Connect the Eureka sensor probe to Plug & Sense! Smart Water Xtreme in any of the sockets shown in the image below.

Figure: Available sockets for the Eureka sensor probe

Maintenance

Calibration

The calibration process is independent for each parameter. Please contact your Sales agent for detailed information. Nevertheless, before carrying out the sensor calibration, please bear in mind the next comments:

• The sensor and the buffer solutions must have the same temperature, so before starting the calibration process leave all the necessary elements in the same temperature conditions. Besides, wait for sensor temperature stabilization once it has been immersed.

• During the sensor measurement, there is a small stabilization time of a few seconds, so please wait until the values remain stable over time.

• The calibration must be done every month to get a reasonable accuracy in the measurements. However, depending on the application, the time between two calibrations would vary. It is highly recommended to do a test as close as possible to the conditions of the final application to check the sensor drift over time. This will allow adjusting the calibration periods according to the required accuracy.

• The buffer solution bottles must be closed properly after usage, to prevent deviations on the default values.

• The sensor needs to be rinsed with clean water before each calibration.

Cleaning the sensor

The Eureka Manta sensor probe needs to be cleaned periodically to remove the possible fouling or other biologic material that could appear in the sensor. Organic deposits present on the sensor lens, such as a biofilm or silt, may cause measurement errors. These deposits should be removed carefully with warm soapy water and a soft sponge. Never use abrasive agents (e.g. scouring sponge). Despite the sensor has its own wiper for probe cleaning, cleaning maintenance tasks can not be omitted.

Finally, if the sensor is not going to be used during a large period, it is important to clean the sensor prior to storing it.

Installation

It is important to think about a few aspects before installing the sensor on the field:

• The sensor body should be easily accessible for cleaning, regular maintenance and calibration.

• The sensor body must be firmly fastened to avoid sensor swing and possible collisions with the surrounding objects that can damage the sensor.

• If the sensor is installed totally immersed, it should be fastened from the body and not from the cable. The cable is not designed to hold the sensor and it could be damaged.

• Avoid bubbles around the sensor.

A complete sensor manual can be found on the manufacturer's website.

Application examples

• Buoy deployments

• Telemetered deployments

• Unattended logging

• Process monitoring

COD, BOD, TOC, SAC254 and temperature StacSense sensor probe

The StacSense sensor probe uses optical technology to measure the ultraviolet spectrum at 254 nm, allowing the measurement of multiple parameters related to the organic water content.

Normally, there are several components related to organic life, so it is usual to obtain the organic matter through parameters like Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), Total Organic Carbon (TOC) and Spectral Absorption Coefficient at 254 nm (SAC254).

The StacSense probes are not recommended for seawater applications. Contact your Sales agent for more information.

Figure: COD, BOD, TOC, SAC254 and temperature StacSense sensor probe

Specifications

• Measurement principle: UV 254 nm absorption

• Compensation: Turbidity at 530 nm. Internal temperature

• Wavelengths: 254 nm (turbidity correction at 530 nm)

• Type of detector: Silicon photodiode

• Optical paths: 2 mm (wastewater) and 50 mm (drinking water)

• Maximum sample rate: 2 seconds

• IP classification: IP68

• Maximum immersion depth: 50 meters

• Maximum pressure: 5 bars

• Operating temperature: 0-40°C

• Storage temperature: -10°C to +50°C

• pH range: pH2 to pH12

• Dimensions: 420 x 50 mm

Measurement ranges:

Optical path	Parameter	Range	Units	Detection limit	Quantification limit	Accuracy
2 mm	SEC254	0-750	Abs/m	1.7	5	1 or ±3%
	CODEQ	0-1300	mg/L	3	9	2 or ±3%
	BODEQ	0-350	mg/L	1	3	1 or ±3%
	TOCEQ	0-500	mg/L	1.5	4	1 or ±3%
	TurbidityEQ	0-500	FAU	1.5	5	5 or ±5%
50 mm	SEC254	0-30	Abs/m	0.2	0.3	0.1 or ±3%
	CODEQ	0-50	mg/L	0.15	0.6	0.2 or ±3%
	BODEQ	0-15	mg/L	0.1	0.2	0.1 or ±3%
	TOCEQ	0-20	mg/L	0.1	0.2	0.1 or ±3%
	TurbidityEQ	0-40	FAU	0.4	1.2	1 or ±7%

Figure: Luminosity sensor graphic

Measurement process

The StacSense sensor provides a digital signal using the SDI-12 protocol.

Reading code:

{
    // 1. Declare an object for the sensor
    Aqualabo_SAC mySensor(XTR_SOCKET_A);
    // 2. Turn ON the sensor
    mySensor.ON();
    // 3. Read the sensor. Values stored in class variables
    // Check complete code example for details
    mySensor.read();
    // 4. Turn off the sensor
    mySensor.OFF();
}

During the sensor measurement, there is a small stabilization time of a few seconds, so it is recommended to wait until the values remain stable over time.

A complete example code for reading this sensor probe can be found on the Development section of our website: https://development.libelium.com/smart-water-xtreme-sensor-guide/sensors-probes

Socket

Connect the StacSense sensor probe to Plug & Sense! Smart Water Xtreme in any of the sockets shown in the image below.

Figure: Available sockets for the Luminosity sensor probe

Maintenance

Calibration

By default, the sensor is factory-calibrated, therefore calibration may not be needed for the 1st usage. However, to increase the sensor accuracy if deviations are detected, calibration would be necessary. Nevertheless, before carrying out the sensor calibration, please bear in mind the next comments:

• The sensor and the buffer solutions must have the same temperature, so before starting the calibration process, leave all the necessary elements in the same temperature conditions. Besides, wait for sensor temperature stabilization once it has been immersed.

• During the sensor measurement, there is a small stabilization time of a few seconds, so please wait until the values remain stable over time.

• The calibration must be done every month to get a reasonable accuracy in the measurements. However, depending on the application, the time between two calibrations would vary. It is highly recommended to do a test as close as possible to the conditions of the final application to check the sensor drift over time. This will allow adjusting the calibration periods according to the required accuracy.

• The buffer solution bottles must be closed properly after usage to prevent deviations from the default values.

• The sensor needs to be rinsed with clean water before each calibration.

Cleaning the sensor

The StacSense sensor probe needs to be cleaned periodically to remove the possible fouling or other biologic material that could appear on the sensor. Organic deposits present on the sensor lens, such as a biofilm or silt, may cause measurement errors. These deposits should be removed carefully with warm soapy water and a soft sponge. Never use abrasive agents (e.g. scouring sponge).

Finally, if the sensor is not going to be used for a long period, it is important to clean the sensor prior to storing it. Remember to place the protection cap together with a moisture absorbent element (like a piece of cotton).

Installation

It is important to think about a few aspects before installing the sensor on the field:

• The sensor body should be easily accessible for cleaning, regular maintenance and calibration.

• The sensor body must be firmly fastened to avoid sensor swing and possible collisions with the surrounding objects that can damage the sensor.

• If the sensor is installed totally immersed, it should be fastened from the body and not from the cable. The cable is not designed to hold the sensor and it could be damaged.

• Avoid bubbles around the sensor.

A complete sensor manual can be found on the manufacturer's website.

Application examples

• Buoy deployments

• Telemetered deployments

• Unattended logging

• Surface water monitoring

• Waste water and drinking water organic matter monitoring

Radar level VEGAPULS C21 sensor probe

The Radar level VEGAPULS C21 sensor provides reliable measurement results under all conditions thanks to its 80 GHz radar technology. Compared to ultrasonic measuring instruments, radar sensors measure unaffected by temperature fluctuations, vacuum or high pressures and are insensitive to contamination.

Due to the high focusing of the 80 GHz technology, the radar beam can be aligned almost precisely to the medium to be measured. It is suitable for use in water treatment, pumping stations and rain overflow basins, for flow measurement in open channels and level monitoring. In bulk solids the sensors are used in small bulk solids silos or open containers.

Figure: Radar level VEGAPULS C21 sensor probe

Specifications

Operation frequency: 80 GHz Maximum detection distance: 15 m Accuracy: ±2 mm Operating temperature: -40 to 80 °C Usage: water or bulk solid tanks Protection rating: IP66/IP68 (3 bar), type 6P Cable length: 5 m

Measurement process

The Radar level VEGAPULS C21 sensor provides a digital signal using the SDI-12 protocol.

Reading code:

{
    // 1. Declare an object for the sensor
    VegaPuls_C21 mySensor(XTR_SOCKET_A);
    // 2. Turn ON the sensor
    mySensor.ON();
    // 3. Read the sensor. Values stored in class variables
    // Check complete code example for details
    mySensor.read();
    // 4. Turn off the sensor
    mySensor.OFF();
}

You can find a complete example code for reading this sensor probe in the following link: https://development.libelium.com/sw-xtr-44-vegapulsC21-sensor-reading

Socket

Connect the Radar level VEGAPULS C21 sensor probe to Plug & Sense! Smart Water Xtreme in the sockets A, B, C or D.

Installation

The Radar level VEGAPULS C21 sensor probe must be focused directly to the point we want to measure. Below there are a couple of examples of installations where the sensor can be used.

Figure: Radar level VEGAPULS C21 sensor installation in a water tank

Figure: Radar level VEGAPULS C21 sensor installation in a grain tank

Application examples

• Water tank measurement

• Bulk solids tank measurement

• Pumping stations

• Rain overflow basins

• Flow measurement in open channels

• River level control

• Early flood detection

• Sea tide monitoring

• Open containers

Calibration solutions

Libelium provides several calibration solutions to calibrate the sensors.

pH Calibration kit

Characteristics:

• 4.0 pH (red), 7.0 pH (yellow), 10.0 pH (blue) ±0.02 pH at 25 ºC • 125 ml each

This kit includes three buffer solutions of 4.0 pH, 7.0 pH and 10.0 pH, of colors red, yellow and blue respectively.

The calibration process is described in section “Calibration procedure”, when handling them pay attention to the information provided in the MSDS

Figure: Image of the pH calibration kit

Conductivity calibration kits

Characteristics:

• 3 kits for K = 0.1, K = 1 and K = 10 • around 0.084 mS, 1.413 mS, 12.88 mS, 80 mS and 150 mS at 25 ºC • 125 ml each

Six solutions for sensor calibration are included within these 3 kits, so the probe can be calibrated in a wide range of conductivities.

Figure: Image of the 3 conductivity calibration kits. Concentration values may vary.

ORP Calibration solution

Characteristics:

• 240 mV ±2 mV at 25 ºC

• 100 ml each

The ORP calibration solution provides a 240 mV output at 25ºC (beware that it may change at different temperatures) which facilitates the adjustment of the sensor output to the actual values of oxidation-reduction potential. Note that this buffer will keep its properties for 30 days once open. It is recommended to store refrigerated.

Figure: Image of the ORP calibration solution

Dissolved Oxygen calibration solution

Characteristics:

• 0mg/ml at 25ºC

• 100ml

In the case of the dissolved oxygen sensor Libelium provides a solution of 0mg/ml adequate to test the sensor. Though it provides a very good approximation for the zero output, it is not recommended for calibration.

Figure: Image of the dissolved oxygen calibration solution

Remember to read carefully the material safety data sheets you can findin the “Safety guides” section of this guide, in order to take the corresponding precautions when manipulating these solutions and dispose them in the appropriate way.

Turbidity calibration Kit

Characteristics:

• 4000 NTU

• 125 ml

The formazine solution of 4000 NTU allows the user to obtain any concentration lower than 4000 NTU by mixing with distilled water, in order to calibrate in the desired range.

Figure: Turbidity calibration solution

Remember to read carefully the material safety data sheets you can find in the "Safety guides" section of this guide, in order to take the corresponding precautions when manipulating these solutions and dispose them in the appropriate way.