Sensors

Starting with the gas sensors

In this section we are going to explain the first steps to start with the sensors used in the Gases PRO Sensor Board.

Notes for Calibrated Gas Sensors

1- Calibrated gas sensors are manufactured once the order has been placed to ensure maximum durability of the calibration feature. Libelium keeps a minimum stock of calibrated gas sensors to ensure the maximum durability. Ensambling process and delivery time takes from 1 to 2 weeks in case the current stock is enough for the order and from 4 to 6 weeks in case the order is higher than the stock available and new sensors units need to be manufactured and calibrated. Please inform as soon as possible of your sensor requirements to our Sales agents so that they can order the units needed to factory.

2- Lifetime of calibrated gas sensors is 6 months working at its maximum accuracy as every sensor looses a small percentage of its original calibration monthly in a range that may go from 0.5% to 2% (depending on the external conditions: humidity, temperature, measured gas concentration, if there are another type of gas present which corrode the sensor, etc). We strongly encourage our customers to buy extra gas sensor probes to replace the originals after that time to ensure maximum accuracy and performance. Any sensor should be understood as a disposable item; that means that after some months it should be replaced by a new unit.- Electrochemical calibrated gas sensors are a good alternative to the professional metering gas stations however they have some limitations. The most important parameters of each sensor are the nominal range and the accuracy. If you need to reach an accuracy of ±0.1 ppm remember not to choose a sensor with an accuracy of ±1 ppm. Take a look in the chapter dedicated to each sensor.

4- Libelium indicates an accuracy for each sensor just as an ideal reference (for example, "±0.1 ppm"). This theoretical figure has been calculated as the best error the user could expect, the optimum case. In real conditions, the measurement error may be bigger (for example, "±0.3 ppm"). The older the sensor is, the more deteriorated it is, so the accuracy gets worse. Also, the more extreme the concentration to meter is, the worse the accuracy is. And also, the more extreme the environmental conditions are, the quicker the sensor decreases its accuracy.

5- In order to increase the accuracy and reduce the response time we strongly recommend to keep the gas sensor board ON as electrochemical sensors have a very low consumption (less than 1 mA). So these sensors should be left powered ON while Waspmote enters into deepsleep mode. Latest code examples implement in the new API of Waspmote v15 follow this strategy. If you are using the old version of the API and boards (v12) write in our Forum and we will help you to modify your code.

6- These sensors need a stabilization time to work properly, in some cases hours. We recommend wait 24hours of functioning (always with the gas sensor board ON) to ensure that the values of the sensors are stable.

7 AFE boards for electrochemical gas sensors have different gain options. The system integrator must choose the adequate gain according to the concentration range to measure. For low concentrations, higher gains are recommended. To know how choosing the right gain, see the chapter "How to choose the right gain resistor".

8- A digital smoothing filter based on previous values is interesting to reduce noise. It will increase the accuracy of the Gases PRO sensors. The filter adequate for its application (note that every sample given by the library has already been filtered inside Waspmote) means from 4 to 8 values.

A simple moving average can be used to increase the accuracy and reduce the noise.

\text{Filtered }\text{value} = \frac{\text{sample}{_t} + \text{sample}_{t - 1} + \text{sample}_{t - 2} + \text{...} + \text{sample}_{t - {(n - 1)}}}{n}

Where:

Filtered value is the concentration value with the mean filter applied
sample are the measurements taken by the gas sensors being sample_t the last measurement, sample_(t-1) the penultimate measurement, etc.
n are the number of samples to calculate the moving mean.

Other filters can be applied according to the project requirements

9- Take into account that developing a robust application for gases detection or measurement may take an important effort of testing and knowing the insights of the sensor probes and code that reads them.

Comparative between Libelium hardware with Alphasense sensors and Alphasense hardware with Alphasense sensors

Ozone

Sensor 1 -Alphasense (blue)

Real Input (ppm)	Medium Measured Value (ppm)	Error (ppm)
0 ppm	-1.641	1.641
1 ppm	-0.815	1.815
6 ppm	5.77	0.221

Sensor 2 - Libelium (red)

Real Input (ppm)	Medium Measured Value (ppm)	Error (ppm)
0 ppm	0.861	0.861
1 ppm	0.210	0.789
6 ppm	7.039	1.039

Sensor 1 -Alphasense (blue)

Real Input (ppm)	Medium Measured Value (ppm)	Error (ppm)
7 ppm	6.182	0.818
2 ppm	1.840	0.160
0 ppm	-0.4098	0.4098

Sensor 2 - Libelium (red)

Real Input (ppm)	Medium Measured Value (ppm)	Error (ppm)
7 ppm	6.478	0.521
2 ppm	1.919	0.08
0 ppm	-0.260	0.260

Sensor 1 -Alphasense (blue)

Real Input (ppm)	Medium Measured Value (ppm)	Error (ppm)
10 ppm	10.76	-0.766
0 ppm	0.826	-0.826
1 ppm	1.718	-0.718

Sensor 2 - Libelium (red)

Real Input (ppm)	Medium Measured Value (ppm)	Error (ppm)
10 ppm	10.66	-0.066
0 ppm	0.790	-0.790
1 ppm	1.636	-0.636

SO2

Sensor 1 -Alphasense (blue)

Real Input (ppm)	Medium Measured Value (ppm)	Error (ppm)
4 ppm	4.183	-0.183
0 ppm	0.373	-0.373
8 ppm	7.85	0.146

Sensor 2 - Libelium (red)

Real Input (ppm)	Medium Measured Value (ppm)	Error (ppm)
4 ppm	4.451	-0.451
0 ppm	0.5779	-0.5779
8 ppm	7.614	0.358

NO2

Sensor 1 - Libelium (red)

Real Input (ppm)	Medium Measured Value (ppm)	Error (ppm)
1 ppm	0.721	0.278
3 ppm	2.776	0.223
0 ppm	-0.163	0.163

Understanding the sensor accuracy and the range of operation

Metering gas concentration in the range of low ppb (close to 0 ppb) is still a complex technical challenge. Electrochemical sensors deliver tiny currents (in nA) which need to be amplified. And like any other electronic system, there is an inherent error inside the sensor signal. This error has 2 mathematical components: the constant error (bias) and a random/unpredictable component too (ripple).

This error is given by the sensor itself. It is complicated to remove the error. The best practice is to calibrate the sensor: our API applies equations with the correction factors calculated by the manufacturer on their gas chambers (these values are unique, obtained for each sensor; the values are hard-coded on a chip soldered on the sensor's AFE). But this calibration may not be enough for certain applications that require extreme accuracy (the customer can create an additional calibration process to meet his special needs, targeting especially the constant error).

Libelium obtained the accuracy value of its sensors experimentally: we visited a chemical laboratory and measured the error our sensors made at different gas concentrations provided by standard gases (with known and controlled ppb). We observed most of Libelium's sensors feature an accuracy as good as ±0.2 ppm in good conditions (or even ±0.1 ppm for certain models). That is, the typical error we measured in these experiments is as low as ±200 ppb in such favorable conditions (±100 ppb in selected top models).

As we can see in the figure above, the red dotted line represents the real concentration of a certain gas. The concentration is not constant over time, but remains in a very low range: it starts at 60 ppb and remains between 70 and 20 ppb. This is a typical range for many pollutant gases (NO2, O3, CO, etc) in not-too-polluted environments, like EU or USA cities.

In the graph we also see 2 green lines. They represent the maximum and minimum readings that we can expect from the Libelium sensor. We obtained these 2 lines easily: we simply added (and subtracted) to the red line (real concentration) the accuracy of the sensor (which we assume here to be 100 ppb). The area between the 2 green lines represents the area of uncertainty: the sensor can give values within this area. This error is inherent to the sensor and cannot be eliminated (additional calibration processes help mitigate it).

A curious effect is the sensor can deliver negative values for the gas concentration. This is common when the sensor is operating at a concentration below to 100 or 200 ppb. Of course, it is physically impossible to have "-40 ppb" of NO2, but on a mathematical level it makes sense: our API's function simply returns a numerical value according to the equation and correcting factors defined by the manufacturer. Previously, our API removed negative values (making them 0 ppb automatically), but we think it is appropriate to give the raw values again, without saturating to 0: this way the user can know that the sensor is working; if negative values are obtained, he knows that the current gas concentration is just below the accuracy of the sensor.

Obviously, the relative error made by the sensor is high at low concentrations: An error of -50 ppb is huge when the gas concentration is 60 ppb. However, the relative error is lower as the concentration increases: a relative error of -50 ppb is almost negligible at 800 ppb.

Understanding the basics of electrochemical sensors

Gas sensors (except the combustible gases sensor and the CO2 sensor) are electrochemical cells that operate in the amperometric mode. That is, they generate a current that is linearly proportional to the fractional volume of the target gas. These sensors are composed of 3 metal strips connecting each electrode to the 3 pins outside of the sensor body and a cell electrolyte. Each electrode has its own specific function:

Working electrode reacts with the target gas to generate a current
Counter electrode supplies a current that balances that generated by the working electrode current
Reference electrode sets the operating potential (bias voltage) of the working electrode

The cell electrolyte provides ionic electrical contact between the electrodes.

To convert the current generated by the working electrode in a voltage for the ADC, the AFE module uses a transimpedance stage with a selectable gain resistor.

The bias voltage is managed by the AFE module and it is automatically fixed by the sensor parameters stored into the EEPROM. These sensors use the 3-electrode AFE board.

The Ozone , Nitric Oxide (low concentrations), Nitric Dioxide (high accuracy) and Sulphur Dioxide (high accuracy) sensors have a 4th electrode. This electrode, commonly called auxiliary electrode, works as an extra working electrode and it is used to compensate the variations produced by the temperature in the baseline current. The compensation will be performed automatically by the API library. These sensors use the 4-electrode AFE board.

Electrochemical sensors have a very low consumption (less than 1 mA) so, to increase the accuracy and reduce the response time, these sensors can keep powered while Waspmote enters into deepsleep mode.

These sensors need a stabilization time to work properly, in some cases hours. It implies that the first reads of the sensors may have an offset level.

Understanding the combustible gas sensor

The CH4 and combustible gases sensor uses the pellistor technology to detect the gas concentration. A pellistor consists of a very fine coil of platinum wire, embedded within a ceramic pellet. On the surface of the pellet there is a layer of a high surface area noble metal, which, when hot, acts as a catalyst to promote exothermic oxidation of flammable gases. In operation, the pellet and so the catalyst layer is heated by passing a current through the underlying coil. In the presence of a flammable gas or vapour, the hot catalyst allows oxidation to occur in a similar chemical reaction to combustion. Just as in combustion, the reaction releases heat, which causes the temperature of the catalyst together with its underlying pellet and coil to rise. This rise in temperature results in a change in the electrical resistance of the coil, and it is this change in electrical resistance which constitutes the signal from the sensor.

Pellistors are always manufactured in pairs, the active catalyzed element being supplied with an electrically matched element which contains no catalyst and is treated to ensure no flammable gas will oxidize on its surface. This "compensator" element is used as a reference resistance to which the sensor's signal is compared, to remove the effects of environmental factors other than the presence of a flammable gas. In the case of the CH-A3 gas sensor from Alphasense, detector and compensator are inside the same encapsulated. One pin of each resistor are connected to a pin of the encapsulated. The other pins are connected together inside the sensor to the signal pin.

The AFE module fixes the supply voltage to the resistors and reads the voltage of the signal pin. This sensor uses the pellistor/NDIR AFE board.

Understanding the CO2 sensor

The IR series of infrared gas detection sensors use the technique of NDIR (Non-Dispersive Infrared) to monitor the presence of hydrocarbons or carbon dioxide. This technique is based on the fact that the gas has a unique and well-defined light absorption curve in the infrared spectrum that can be used to identify the specific gas. The gas concentration can be determined by using a suitable infrared source and analyzing the optical absorption of the light that passes through the gas. The IRSS-E sensor contains the same optics as the related and simpler model IRSS-X, but is also equipped with incorporated electronics and software in order to provide an output that is linearized and temperature compensated.

In the standard version of IRSS-E, the sensor provides a linearized and temperature compensated analog voltage output that is proportional to the gas concentration. The AFE module sets the supply voltage and reads the voltage of the signal pin. This sensor uses the pellistor/NDIR AFE board.

Lifetime of the Gas sensors

All sensors provided by Libelium for the Gases PRO Sensor Board have been calibrated in the origin factory by the manufacturer. Calibration parameters are stored inside the EEPROM (non-volatile memory) of each AFE board for a unique gas sensor. Thus, changing the AFE boards between gas sensors is forbidden.

The maximum accuracy for each sensor is valid only for 6 months. Every sensor loses a small percentage of its original calibration monthly in a range that may go from 0.5% to 2%.

Calibrated gas sensors are manufactured once the order has been placed to ensure maximum durability of the calibration feature. Manufacturing process and delivery may take from 4 to 6 weeks. Lifetime of calibrated gas sensors is 6 months working at maximum accuracy. We strongly encourage our customers to buy extra gas sensor probes to replace the originals after that time to ensure maximum performance.

Remember that damages caused by external agents (animals, fire, flooding, gases, etc) are not covered under the Warranty. High concentration of corrosive gases (for example, NH3 -ammonia-, present in pig farms due to swine manure), causes early degradation of the devices, especially the most sensitive or exposed ones, such as sensors.

Libelium indicates an accuracy for each sensor just as an ideal reference (for example, "±50 ppm"). This theoretical figure has been calculated as the best error the user could expect, the optimum case. In real conditions, the measurement error will be bigger (for example, "±90 ppm"). As stated before, the older the sensor is, the more deteriorated it is, so the accuracy gets worse. Also, the more extreme the concentration to meter is, the worse the accuracy is. And also, the more extreme the environmental conditions are, the quicker the sensor ages. The sensors have been tested at 20 ºC / 101300 Pa. Cross sensitivity gases are not target gases. Relation can change with aging. The cross sensitivity may fluctuate between +/- 30% and may differ from batch to batch or from sensor's lifetime. The cross sensitivities are including but not limited to the gases from the tables. It may also respond to other gases. The data offered solely for consideration, investigation, and verification. Any use of these data and information must be determined by the user to be in accordance with federal, state, and local laws and regulations. Specifications are subject to change without notice.

Temperature, Humidity and Pressure sensor

The BME280 is a digital temperature, humidity and pressure sensor developed by Bosch Sensortec.

Specifications

Electrical characteristics

Supply voltage: 3.3 V Sleep current typical: 0.1 μA Sleep current maximum: 0.3 μA

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) Typical consumption: 1 μA measuring

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 Typical consumption: 1.8 μA measuring Maximum consumption: 2.8 μA measuring

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) Typical consumption: 2.8 μA measuring Maximum consumption: 4.2 μA measuring

You can find a complete example code for reading the Temperature, Humidity and Pressure sensor in the following link:

GP v30 05: Temperature, humidity and pressure sensorGP v30 05 – Temperature, humidity and pressure sen

Carbon Monoxide (CO) Gas Sensor for high concentrations [Calibrated]

This sensor was discontinued in 2017. Its substitute is the Carbon Monoxide (CO) Gas Sensor for high concentrations [Calibrated]. The information about this alternative sensor can be found in the next section of this guide.

Specifications

Gas: CO Sensor: 4-CO-500

Performance Characteristics Nominal Range: 0 to 500 ppm Maximum Overload: 2000 ppm Long Term Output Drift: < 2% signal/month Response Time (T90): ≤ 30 seconds Sensitivity: 70 ± 15 nA/ppm Accuracy: as good as ±1 ppm* (ideal conditions)

Operation Conditions Temperature Range: -20 ºC to 50 ºC Operating Humidity: 15 to 90% RH non-condensing Pressure Range: 90 to 110 kPa Storage Temperature: 0 ºC to 20 ºC Expected Operating Life: 5 years in air

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

The electrochemical sensors must be always powered on in order to get optimum measurements. This implies a power consumption, however it improves the performance of the sensor. This should also be applied when entering sleep modes so the sensor is not powered off selecting the proper sleep option.

Calibrated gas sensors are manufactured once the order has been placed to ensure maximum durability of the calibration feature. The manufacturing process and delivery may take from 4 to 6 weeks. The lifetime of calibrated gas sensors is 6 months working at maximum accuracy. We strongly encourage our customers to buy extra gas sensors to replace the original ones after that time to ensure maximum accuracy and performance.

Cross-sensitivity data

Gas	Formula	Concentration (ppm)	Output Signal (ppm CO equivalent)
Hydrogen Sulfide	H2S	24	0
Sulfur Dioxide	SO2	5	0
Cholrine	Cl2	10	0-1
Nitric Oxide	O2	25	0
Nitric Dioxide	NO2	5	0
Hydrogen	H2	100	40
Ethylene	C2H4	100	16

You can find a complete example code for reading the CO Sensor for high concentrations in the following link:

Carbon Monoxide (CO) Gas Sensor for low concentrations [Calibrated]

Specifications

Gas: CO Sensor: CO-A4

Performance Characteristics Nominal Range: 0 to 25 ppm Maximum Overload: 2000 ppm Long Term Sensitivity Drift: < 10% change/year in lab air, monthly test Long Term zero Drift: < ±100 ppb equivalent change/year in lab air Response Time (T90): ≤ 20 seconds Sensitivity: 220 to 375 nA/ppm Accuracy: as good as ±0.1 ppm* (ideal conditions) H2S filter capacity: 250000 ppm·hrs

Operation Conditions Temperature Range: -30 ºC to 50 ºC Operating Humidity: 15 to 90% RH non-condensing Pressure Range: 80 to 120 kPa Storage Temperature: 0 ºC to 20 ºC Expected Operating Life: 3 years in air

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

* Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

* Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Gas

Formula

Concentration (ppm)

Output Signal (ppm CO equivalent)

Hydrogen Sulfide

H2S

< 0.1

Sulfur Dioxide

SO2

< -2

Cholrine

Cl2

< 0.1

Nitric Oxide

< -2

Sulfur Dioxide

NO2

< 0.1

Hydrogen

100

< 10

Ethylene

C2H4

100

< 0.5

Ammonia

NH 3

< 0.1

You can find a complete example code for reading the CO Sensor for low concentrations in the following link:

Carbon Dioxide (CO2) Gas Sensor [Calibrated]

Specifications

Gas: CO2 Sensor: INE20-CO2P-NCVSP

Performance Characteristics Nominal Range: 0 to 5000 ppm Long Term Output Drift: < ± 250 ppm/year Warm up time: 60 seconds @ 25 ºC At least 30 min for full specification @ 25 °C Response Time (T90): ≤ 60 seconds Resolution: 25 ppm Accuracy: as good as ±50 ppm*, from 0 to 2500 ppm range (ideal conditions) as good as ±200 ppm*, from 2500 to 5000 ppm range (ideal conditions)

Operation Conditions Temperature Range: -40 ºC to 60 ºC Operating Humidity: 0 to 95% RH non-condensing Storage Temperature: -40 ºC to 85 ºC MTBF: ≥ 5 years

Sockets for Waspmote OEM:

SOCKET_1

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: 80 mA

The CO2 Sensor and the Methane (CH4) and Combustible Gas Sensor have high power requirements and cannot work together in the same Gases PRO Sensor Board. The user must choose one or the other, but not both.

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

You can find a complete example code for reading the CO2 Sensor in the following link:

Molecular Oxygen (O2) Gas Sensor [Calibrated]

Specifications

Gas: O2 Sensor: LFO2-A4

Performance Characteristics Long Term Output Drift: < 1% signal/3 months Response Time (T90): ≤ 17 seconds Sensitivity: 80-130 μA @ 20.9% O2 Accuracy: as good as ±0.1% (ideal conditions)

Operation Conditions Temperature Range: -30 ºC to 50 ºC Operating Humidity: 5 to 95% RH non-condensing Pressure Range: 80 to 120 kPa Storage Temperature: 3 ºC to 20 ºC, 6 months Expected Operating Life: 2 years until 85% original output of 20.9% O2

Note: Previously, Libelium offered the equivalent O2 sensor 4-OL, by Eurogas.

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

You can find a complete example code for reading the O2 Sensor in the following link:

Ozone (O3) Gas Sensor [Calibrated]

Specifications

Gas: O3 Sensor: OX-A431

Performance Characteristics Nominal Range: 0 to 18 ppm Maximum Overload: 50 ppm Long Term sensitivity Drift: -20 to -40% change/year Response Time (T90): ≤ 45 seconds Sensitivity: -200 to -550 nA/ppm Accuracy: as good as ±0.2 ppm* (ideal conditions) High cross-sensitivity with NO2 gas. Correction could be necessary in ambients with NO2.

Operation Conditions Temperature Range: -30 ºC to 40 ºC Operating Humidity: 15 to 85% RH non-condensing Pressure Range: 80 to 120 kPa Storage Temperature: 3 ºC to 20 ºC Expected Operating Life: > 24 months in air

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Gas

Formula

Concentration (ppm)

Output Signal (ppm CO equivalent)

Hydrogen Sulfide

H2S

< 10

Nitric Dioxide

NO2

70 to 120

Cholrine

Cl2

< 30

Nitric Oxide

< 3

Sulfur Dioxide

SO2

< -6

Carbon Monoxide

< 0.1

Hydrogen

100

< 0.1

Ethylene

C2H4

100

< 0.1

Ammonia

NH3

< 0.1

Carbon Dioxide

CO2

50000

0.1

Halothane

100

< 0.1

This sensor has a very high cross-sensitivity with NO2 gas. So, the output in ambients with NO2 will be a mix of O3 and NO2. A simple way to correct this effect is to subtract NO2 concentration from O3 concentration with an NO2 gas sensor. The measure from the NO2 sensor must be accurate in order to subtract the right value. See the related section in the "Library for gas sensors" chapter to use the right function.

You can find a complete example code for reading the O3 Sensor in the following link:

GP v30 01: Electrochemical gas sensorsGP v30 01 – Electrochemical gas sensors

Nitric Oxide (NO) Gas Sensor for high concentrations [Calibrated]

This sensor was discontinued in March 2017. Its substitute is the Nitric Monoxide (NO) for low concentrations Gas Sensor [Calibrated]. The information about this alternative sensor can be found in the next section of this guide.

Specifications

Gas: NO Sensor: 4-NO-250

Performance Characteristics Nominal Range: 0 to 250 ppm Maximum Overload: 1000 ppm Long Term Output Drift: < 2% signal/month Response Time (T90): ≤ 30 seconds Sensitivity: 400 ± 80 nA/ppm Accuracy: as good as ±0.5 ppm* (ideal conditions)

Operation Conditions Temperature Range: -20 ºC to 50 ºC Operating Humidity: 15 to 90% RH non-condensing Pressure Range: 90 to 110 kPa Storage Temperature: 0 ºC to 20 ºC Expected Operating Life: 2 years in air

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Gas	Formula	Concentration (ppm)	Output signal (ppm NO equivalent)
Carbon Monoxide	CO	300	0
Sulfur Dioxide	SO2	5	0
Nitric Dioxide	NO2	5	1.5
Hydrogen Sulfide	H2S	15	-1.5

You can find a complete example code for reading the NO Sensor for high concentrations in the following link:

Nitric Oxide (NO) Gas Sensor for low concentrations [Calibrated]

Specifications

Gas: NO Sensor: NO-A4

Performance Characteristics Nominal Range: 0 to 18 ppm Maximum Overload: 50 ppm Long Term Sensitivity Drift: < 20% change/year in lab air, monthly test Long Term zero Drift: 0 to 50 ppb equivalent change/year in lab air Response Time (T90): ≤ 25 seconds Sensitivity: 350 to 550 nA/ppm Accuracy: as good as ±0.2 ppm* (ideal conditions)

Operation Conditions Temperature Range: -30 ºC to 50 ºC Operating Humidity: 15 to 85% RH non-condensing Pressure Range: 80 to 120 kPa Storage Temperature: 0 ºC to 20 ºC Expected Operating Life: 2 years in air

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Gas	Formula	Concentration (ppm)	Output Signal (ppm NO equivalent)
Hydrogen Sulfide	H2S	15	-1.5
Sulfur Dioxide	SO2	5	0
Cholrine	Cl2	5	1.5
Carbon Monoxide	CO	300	0

You can find a complete example code for reading the NO Sensor for low concentrations in the following link:

Nitric Dioxide (NO2) Gas Sensor [Calibrated]

This sensor was discontinued in May 2017. Its substitute is the Nitric Dioxide (NO2) high accuracy Gas Sensor [Calibrated]. The information about this alternative sensor can be found in the next section of this guide.

Specifications

Gas: NO2 Sensor: 4-NO2-20

Performance Characteristics Nominal Range: 0 to 20 ppm Maximum Overload: 250 ppm Long Term Output Drift: < 2% signal/month Response Time (T90): ≤ 30 seconds Sensitivity: 600 ± 150 nA/ppm Accuracy: as good as ±0.2 ppm* (ideal conditions)

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Gas	Formula	Concentration (ppm)	Output Signal (ppm NO equivalent)
Carbon Monoxide	CO	300	0
Hydrogen Sulfide	H2S	15	-1.2
Sulfur Dioxide	SO2	5	-5
Nitric Oxide	NO	35	0
Chlorine	Cl2	1	-1

You can find a complete example code for reading the NO2 Sensor in the following link:

Nitric Dioxide (NO2) high accuracy Gas Sensor [Calibrated]

Specifications

Gas: NO2 Sensor: NO2-A43F

Performance Characteristics Nominal Range: 0 to 20 ppm Maximum Overload: 50 ppm Long Term Sensitivity Drift: < -20 to -40% change/year in lab air, monthly test Long Term zero Drift: < 20 ppb equivalent change/year in lab air Response Time (T90): ≤ 60 seconds Sensitivity: -175 to -450 nA/ppm Accuracy: as good as ±0.1 ppm* (ideal conditions) O3 filter capacity @ 2 ppm: > 500 ppm·hrs

Operation Conditions

Temperature Range: -30 ºC to 40 ºC Operating Humidity: 15 to 85% RH non-condensing Pressure Range: 80 to 120 kPa Storage Temperature: 0 ºC to 20 ºC Expected Operating Life: 2 years in air

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Gas

Formula

Concentration (ppm)

Output Signal (ppm NO2 equivalent)

Hydrogen Sulfide

H2S

< -80

Cholrine

Cl2

< 75

Nitric Oxide

< 5

Sulfur Dioxide

SO2

< -5

Carbon Monoxide

< -5

Hydrogen

100

< 0.1

Ethylene

C2H4

100

< 1

Ammonia

NH3

< 0.2

Carbon Dioxide

CO2

5% vol

0.1

Halothane

100

You can find a complete example code for reading the high accuracy NO2 Sensor in the following link:

Sulfur Dioxide (SO2) Gas Sensor [Calibrated]

This sensor was discontinued in March 2017. Its substitute is the Sulfur Dioxide (SO2) high accuracy Gas Sensor [Calibrated]. The information about this alternative sensor can be found in the next section of this guide.

Specifications

Gas: SO2 Sensor: 4-SO2-20

Performance Characteristics Nominal Range: 0 to 20 ppm Maximum Overload: 150 ppm Long Term Output Drift: < 2% signal/month Response Time (T90): ≤ 45 seconds Sensitivity: 500 ± 150 nA/ppm Accuracy: as good as ±0.2 ppm* (ideal conditions)

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Gas	Formula	Concentration (ppm)	Output Signal (ppm SO2 equivalent)
Carbon Monoxide	CO	300	3
Hydrogen Sulfide	H2S	15	0
Nitric Oxide	NO	35	0
Nitric Dioxide	NO2	5	-5

You can find a complete example code for reading the SO2 Sensor in the following link:

Sulfur Dioxide (SO2) high accuracy Gas Sensor [Calibrated]

Specifications

Gas: SO2 Sensor: SO2-A4

Performance Characteristics Nominal Range: 0 to 20 ppm Maximum Overload: 100 ppm Long Term Sensitivity Drift: < ±15% change/year in lab air, monthly test Long Term zero Drift: <±20 ppb equivalent change/year in lab air Response Time (T90): ≤ 20 seconds Sensitivity: 320 to 480 nA/ppm Accuracy: as good as ±0.1 ppm* (ideal conditions)

Operation Conditions Temperature Range: -30 ºC to 50 ºC Operating Humidity: 15 to 90% RH non-condensing Pressure Range: 80 to 120 kPa Storage Temperature: 0 ºC to 20 ºC Expected Operating Life: 2 years in air

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Gas

Formula

Concentration (ppm)

Output Signal (ppm SO2 equivalent)

Hydrogen Sulfide

H2S

< 40

Cholrine

Cl2

< -70

Nitric Oxide

< -160

Sulfur Dioxide

SO2

< 1.5

Carbon Monoxide

< 2

Hydrogen

100

< 1

Ethylene

C2H4

100

< 1

Ammonia

NH3

< 0.1

Carbon Dioxide

CO2

5% vol

< 0.1

You can find a complete example code for reading the high accuracy SO2 Sensor in the following link:

Ammonia (NH3) Gas Sensor for low concentrations [Calibrated]

Specifications

Gas: NH3 Sensor: 4-NH3-100

Performance Characteristics Nominal Range: 0 to 100 ppm Long Term Output Drift: < 2% signal/month Response Time (T90): ≤ 90 seconds Sensitivity: 135 ± 35 nA/ppm Accuracy: as good as ±0.5 ppm* (ideal conditions)

Operation Conditions

Temperature Range: -20 ºC to 50 ºC Operating Humidity: 15 to 90% RH non-condensing Pressure Range: 90 to 110 kPa Storage Temperature: 0 ºC to 20 ºC Expected Operating Life: ≥1 year in air

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Gas	Formula	Concentration (ppm)	Output Signal (ppm NH3 equivalent)
Carbon Monoxide	CO	300	0
Hydrogen Sulfide	H2S	5	1.5
Carbon Dioxide	CO2	5	-3
Hydrogen	H2	15	30
Isobutylene		35	-1
Ethanol		100	0

You can find a complete example code for reading the NH3 Sensor for low concentrations in the following link:

GP v30 01: Electrochemical gas sensorsGP v30 01 – Electrochemical gas sensors

Ammonia (NH3) Gas Sensor for high concentrations [Calibrated]

Specifications

Gas: NH3 Sensor: 4-NH3-500

Performance Characteristics Nominal Range: 0 to 500 ppm Long Term Output Drift: < 10 % signal per 6 months Response Time (T90): ≤ 90 seconds Sensitivity: 135 ± 35 nA/ppm Accuracy: as good as ±3 ppm* (ideal conditions)

Operation Conditions Temperature Range: -20 ºC to 40 ºC Operating Humidity: 15 to 90% RH non-condensing Pressure Range: 90 to 110 kPa Storage Temperature: 0 ºC to 20 ºC Expected Operating Life: ≥1 year in air

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Gas	Formula	Concentration (ppm)	Output Signal (ppm NH3 equivalent)
Carbon Monoxide	CO	50	-1
Hydrogen Sulfide	H2S	25	1.5
Carbon Dioxide	CO2	5000	-3
Hydrogen	H2	1000	30
Isobutylene	C4H8	100	-1
Ethanol	C2H6O	1000	0
Sulphur Dioxide	SO2	5	8
Nitric Oxide	NO	35	0
Nitric Dioxide	NO2	5	-5
Chlorine	CL2	10	-5

You can find a complete example code for reading the NH3 Sensor for high concentrations in the following link:

GP v30 01: Electrochemical gas sensorsGP v30 01 – Electrochemical gas sensors

Methane (CH4) and Combustible Gases Sensor [Calibrated]

Specifications

Main gas: Methane CH4 Sensor: CH-A3

Performance Characteristics Nominal Range: 0 to 100% LEL methane Long Term Output Drift: < 2% signal/month Response Time (T90): ≤ 30 seconds Accuracy: as good as ±0.15% LEL* (ideal conditions)

Operation Conditions Temperature Range: -40 ºC to 55 ºC Expected Operating Life: 2 years in air

Inhibition/Poisoning

Gas

Formula

Conditions

Effect

Chlorine

CL2

2hrs 20ppm Cl 2 , 50 % sensitivity loss, 2 day recovery

< 10% loss

Hydrogen Sulfide

H2S

12hrs 40ppm H 2 S, 50 % sensitivity loss, 2 day recovery

< 50% loss

HMDS

9 hrs @ 10ppm HMDS

50% activity loss

Sockets for Waspmote OEM:

SOCKET_1

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: 68 mA

The Methane (CH4) and Combustible Gas Sensor and the CO2 Sensor have high power requirements and cannot work together in the same Gases PRO Sensor Board. The user must choose one or the other, but not both.

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Sensitivity data

Hydrocarbon/Gas

% Sensitivity relative to Methane

% LEL Sensitivity to Methane

Hydrogen

130 to 140

160 to 175

Propane

150 to 190

350 to 450

Butane

150 to 180

420 to 500

n-Pentane

180 to 200

600 to 670

Nonane

150 to 170

800 to 950

Carbon Monoxide

42 to 44

17 to 18

Acetylene

150 to 170

300 to 340

Ethylene

150 to 170

270 to 320

Isobutylene

180 to 200

450 to 500

The exact values of these combustible gases cannot be obtained directly. However, it is possible to obtain the other combustible gases values by activating the debug mode in the WaspSensorGas_Pro.h library: take the following data that will be printed by serial monitor (SENSITIVITY: mV/% LEL) and use it along with the sensitivity values of the table above to calculate them.

You can find a complete example code for reading the Methane (CH4) and Combustible Gases Sensor in the following link:

GP v30 03: Pellistor gas sensorsGP v30 03 – Pellistor gas sensors

Molecular Hydrogen (H2) Gas Sensor [Calibrated]

This sensor was discontinued in 2019.

Specifications

Gas: H2 Sensor: 4-H2-1000

Performance Characteristics Nominal Range: 0 to 1000 ppm Maximum Overload: 2000 ppm Long Term Output Drift: < 2% signal/month Response Time (T90): ≤ 70 seconds Sensitivity: 20 ± 10 nA/ppm Accuracy: as good as ±10 ppm* (ideal conditions)

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Gas	Formula	Concentration (ppm)	Output Signal (ppm H2 equivalent)
Hydrogen Sulfide	H2S	24	0
Cholrine	Cl2	10	0
Nitric Oxide	NO	35	10
Sulfur Dioxide	SO2	5	0
Carbon Monoxide	CO	50	200
Nitric Dioxide	NO2	5	0
Ethylene	C2H4	100	80

You can find a complete example code for reading the H2 Sensor in the following link:

Hydrogen Sulfide (H2S) Gas Sensor [Calibrated]

Specifications

Gas: H2S Sensor: 4-H2S-100

Performance Characteristics Nominal Range: 0 to 100 ppm Maximum Overload: 500 ppm Long Term Output Drift: < 2% signal/month Response Time (T90): ≤ 20 seconds Sensitivity: 800 ± 200 nA/ppm Accuracy: as good as ±0.1 ppm* (ideal conditions)

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Gas

Formula

Concentration (ppm)

Output Signal (ppm H2S equivalent)

Ethanol

C2H6O

5000

+/- 1.5

Nitric Dioxide

NO2

-1

Nitric Oxide

Sulfur Dioxide

SO2

Carbon Monoxide

< 6

Hydrogen

10000

Ethylene

C2H4

100

You can find a complete example code for reading the H2S Sensor in the following link:

GP v30 01: Electrochemical gas sensorsGP v30 01 – Electrochemical gas sensors

Hydrogen Chloride (HCl) Gas Sensor [Calibrated]

This sensor was discontinued in 2019.

Specifications

Gas: HCl Sensor: 4-HCl-50

Performance Characteristics Nominal Range: 0 to 50 ppm Maximum Overload: 100 ppm Long Term Output Drift: < 2% signal/month Response Time (T90): ≤ 70 seconds Sensitivity: 300 ± 100 nA/ppm Accuracy: as good as ±1 ppm* (ideal conditions)

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Gas	Formula	Concentration (ppm)	Output Signal (ppm HCL equivalent)
Hydrogen Sulfide	H2S	25	130
Nitric Oxide	NO	20	50
Nitric Dioxide	NO2	10	1
Sulfur Dioxide	SO2	20	35
Carbon Monoxide	CO	100	0
Hydrogen	H2	2000	0
Nitrogen	N	1000000	0

You can find a complete example code for reading the HCl Sensor in the following link:

GP v30 01: Electrochemical gas sensorsGP v30 01 – Electrochemical gas sensors

Hydrogen Cyanide (HCN) Gas Sensor [Calibrated]

This sensor was discontinued in 2019.

Specifications

Gas: HCN Sensor: 4-HCN-50

Performance Characteristics Nominal Range: 0 to 50 ppm Maximum Overload: 100 ppm Long Term Output Drift: < 2% signal/month Response Time (T90): ≤ 120 seconds Sensitivity: 100 ± 20 nA/ppm Accuracy: as good as ±0.2 ppm* (ideal conditions)

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Gas	Formula	Concentration (ppm)	Output Signal (ppm HCN equivalent)
Nitric Dioxide	NO2	5	-3
Nitric Oxide	NO	35	-1
Sulfur Dioxide	SO2	5	1.5
Carbon Monoxide	CO	300	0
Ethylene	C2H4	100	0
Hydrogen Sulfide	H2S	15	30

You can find a complete example code for reading the HCN Sensor in the following link:

Phosphine (PH3) Gas Sensor [Calibrated]

This sensor was discontinued in 2019.

Specifications

Gas: PH3 Sensor: 4-PH3-20

Performance Characteristics Nominal Range: 0 to 20 ppm Maximum Overload: 100 ppm Long Term Output Drift: < 2% signal/month Response Time (T90): ≤ 60 seconds Sensitivity: 1400 ± 600 nA/ppm Accuracy: as good as ±0.1 ppm* (ideal conditions)

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Gas	Formula	Concentration (ppm)	Output Signal (ppm PH3 equivalent)
Sulfur Dioxide	SO2	5	0.9
Carbon Monoxide	CO	1000	0
Ethylene	C2H4	100	0
Hydrogen Sulfide	H2S	15	12
Hydrogen	H2	1000	0
Ammonia	NH3	50	0

You can find a complete example code for reading the PH3 Sensor in the following link:

GP v30 01: Electrochemical gas sensorsGP v30 01 – Electrochemical gas sensors

Ethylene Oxide (ETO) Gas Sensor [Calibrated]

This sensor was discontinued in 2019.

Specifications

Gas: ETO Sensor: 4-ETO-100

Performance Characteristics Nominal Range: 0 to 100 ppm Long Term Sensitivity Drift: < 2% signal/month Response Time (T90): ≤ 120 seconds Sensitivity: 250 ± 125 nA/ppm Accuracy: as good as ±1 ppm* (ideal conditions)

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Hydrocarbon/Gas

Formula

Sensitivity

Ethylene Oxide

ETO

1.0

Carbon Monoxide

2.5

Ethanol

C2H6O

2.0

Methanol

CH4O

0.5

Isopropanol

C3H8O

5.0

i-Butylene

2.5

Butadiene

C4H6

0.9

Ethylene

C2H4

0.8

Propene

C3H6

1.7

Vinyl Chloride

C2H3Cl

1.3

Vinyl Acetate

C4H6O2

2.0

Formic Acid

CH2O2

3.3

Ethyl ether

(C2H5 ) 2O

2.5

Formaldehyde

CH2O

1.0

You can find a complete example code for reading the ETO Sensor in the following link:

GP v30 01: Electrochemical gas sensorsGP v30 01 – Electrochemical gas sensors

Chlorine (Cl2) Gas Sensor [Calibrated]

Specifications

Gas: Cl2 Sensor: 4-Cl2-50

Performance Characteristics Nominal Range: 0 to 50 ppm Maximum Overload: 100 ppm Long Term Output Drift: < 2% signal/month Response Time (T90): ≤ 30 seconds Sensitivity: 450 ± 200 nA/ppm Accuracy: as good as ±0.1 ppm* (ideal conditions)

Sockets for Waspmote OEM:

SOCKET_1
SOCKET_2
SOCKET_3
SOCKET_4
SOCKET_5
SOCKET_6

Sockets for Plug & Sense!:

SOCKET_A
SOCKET_B
SOCKET_C
SOCKET_F

Average consumption: less than 1 mA

*Accuracy values are only given for the optimum case. See the "Calibration" chapter for more detail.

Cross-sensitivity data

Gas	Formula	Concentration (ppm)	Output Signal (ppm CL2 equivalent)
Hydrogen Sulfide	H2S	20	-4
Nitric Oxide	NO	35	0
Nitric Dioxide	NO2	10	12
Sulfur Dioxide	SO2	20	0
Carbon Monoxide	CO	100	0
Hydrogen	H2	3000	0
Ammonia	NH3	100	0
Carbon Dioxide	CO2	10000	0
Chlorine Dioxide	ClO2	1	3.5

You can find a complete example code for reading the Cl2 Sensor in the following link:

GP v30 01: Electrochemical gas sensorsGP v30 01 – Electrochemical gas sensors

Ultrasound Sensor (MaxSonar® from MaxBotix™)

Specifications

I2CXL-MaxSonar®-MB7040™

Operation frequency: 42 kHz Maximum detection distance: 765 cm Interface: Digital bus Consumption (average): 2.1 mA Consumption (peak): 50 mA Usage: Indoors and outdoors (IP-67)

Only one MB7040 sensor is supported.

In the figure below we can see a diagram of the detection range of the sensor developed using different detection patterns (a 0.63 cm diameter dowel for diagram A, a 2.54 cm diameter dowel for diagram B, an 8.25cm diameter rod for diagram C and a 28 cm wide board for diagram D):

I2CXL-MaxSonar®-MB1202™

Operation frequency: 42 kHz Maximum detection distance: 765 cm Interface: Digital bus Consumption (average): 2 mA Consumption (peak): 50 mA Usage: Indoors

Only one MB1202 sensor is supported

In the figure below we can see a diagram of the detection range of the sensor developed using different detection patterns (a 0.63 cm diameter dowel for diagram A, a 2.54 cm diameter dowel for diagram B, an 8.25 cm diameter rod for diagram C and a 28 cm wide board for diagram D):

Measurement process

The MaxSonar® sensors from MaxBotix can connects through digital bus interface. In the next figure, we can see a drawing of two example applications for the ultrasonic sensors, such as liquid level monitoring or presence detection.

The MB7040 sensor is endowed with an IP-67 casing, so it can be used in outdoors applications, such as liquid level monitoring in storage tanks. Below a sample code to measure with the ultrasound sensors is shown:

Reading code:

{
    uint16_t distance;
    distance = Ultrasound.getDistance();
}

You can find a complete example code for reading the distance in the following link:

GP v30 06: Ultrasound sensorGP v30 06 – Ultrasound sensor

Socket

These sensors share the sockets with the Temperature, Humidity and Pressure sensor. The pin correspondence, highlighted in the figure below, is the same for both.

Luminosity sensor (TSL2561)

Specifications

Electrical characteristics Dynamic range: 0.1 to 40000 lux Spectral range: 300 ~ 1100 nm. Voltage range: 2.7 ~ 3.6 V Supply current typical: 0.24 mA Sleep current maximum: 0.3 μA Operating temperature: -30 ~ +70 ºC

Only one TSL2561 sensor is supported

Measurement process

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.

Reading code:

{
    // Read luxes
    luxes = TSL.getLuxes();
}

You can find a complete example code for reading the luminosity in the following link:

GP v30 07: Luxes sensorGP v30 07 – Luxes sensor

Socket

In the image below we can see highlighted the four pins of the terminal block where the sensor must be connected to the board. The white dot luxes board, must match the mark of the Gases PRO Sensor Board.

Particle Matter (PM1 / PM2.5 / PM10) - Dust Sensor

Since February 2019, the OPC-N3 sensor is supplied instead of the OPC-N2. The OPC-N3 has taken the success of the older OPC-N2 unit and has improved it further. With the same dimensions and power/ interface as the N2, the OPC-N3 now measures from 0.35 μm to 40 μm, sorting into 24 size bins. Features include improved aerodynamics with reduction of particle deposition, better low end performance, extended upper size measurements and high/low flow rate digital selection. The OPC-N3 can measure from clean rooms to pollution levels to 2,000 μg/m3 with the unique feature of being able to size classify pollen.

Specifications

Sensor: OPC-N3

Performance characteristics Laser classification: Class 1 as enclosed housing Particle range (μm): 0.35 to 40 spherical equivalent size (based on RI of 1.5, S of 1.65) Size categorization (standard): 24 software bins Sampling interval (seconds): 1 to 30 histogram period Total flow rate: 5.5 L/min Sample flow rate: 280 mL/min Max particle count rate: 10000 particles/second Max coincidence probability: 0.84% at 10,000,000 particles/L - 0.24% at 500 particles/L

Power characteristics Measurement mode (laser and fan on): 270 mA @ 5 V (typical) Voltage range: 4.8 to 5.2 V DC

Enclosure Waterproof Dimensions: 122 x 82 x 85 mm (without fixing lugs) Material: Polycarbonate Cable length: 0.6 m

Operation Conditions Temperature range: -10 ºC to 50 ºC Operating humidity: 0 to 99% RH non-condensing

This sensor has a high current consumption. It is very important to turn on the sensor to perform a measure and then, turn it off to save battery. Also, it is advised to operate with a minimum battery level of 40%, just to avoid voltage drops (due to high current peaks) which could lead to resets in the system.

Dust, dirt or pollen may be accumulated inside the dust sensor structure, especially when the sensor is close to possible solid particle sources: parks, construction works, deserts. That is why it is highly recommended to perform maintenance/cleaning tasks in order to have accurate measures. This maintenance/cleaning frequency may vary depending on the environment conditions or amount of obstructing dust. In clean atmospheres or with low particle concentrations, the maintenance/cleaning period will be longer than a place with a high particle concentrations.

Important note: Do not handle the stickers seals of the enclosure (Warranty stickers). Their integrity is the proof that the sensor enclosure has not been opened. If they have been handled, damaged or broken, the warranty is automatically void.

DO NOT remove the external housing: this not only ensures the required airflow, also protects the user from the laser light. Removal of the casing may expose the user to Class 3B laser radiation. You must avoid exposure to the laser beam. Do not use if the outer casing is damaged. Return to Libelium. Removal of the external housing exposes the OPC circuitry which contains components that are sensitive to static discharge damage.

Note: The Particle Matter (PM1 / PM2.5 / PM10) -- Dust Sensor is available only for the Plug & Sense! line.

Particle matter: the parameter

Particle matter is composed of small solid or liquid particles floating in the air. The origin of these particles can be the industrial activity, exhaust fumes from diesel motors, building heating, pollen, etc. This tiny particles enter our bodies when we breath. High concentrations of particle matter can be harmful for humans or animals, leading to respiratory and coronary diseases, and even lung cancer. That is why this is a key parameter for the Air Quality Index.

Some examples:

Cat allergens: 0.1-5 μm
Pollen: 10-100 μm
Germs: 0.5-10 μm
Oil smoke: 1-10 μm
Cement dust: 5-100 μm
Tobacco smoke: 0.01-1 μm

The smaller the particles are, the more dangerous, because they can penetrate more in our lungs. Many times, particles are classified:

PM1: Mass (in μg) of all particles smaller than 1 μm, in 1 m³.
PM2.5: Mass (in μg) of all particles smaller than 2.5 μm, in 1 m³.
PM10: Mass (in μg) of all particles smaller than 10 μm, in 1 m³.

Many countries and health organizations have studied the effect of the particle matter in humans, and they have set maximum thresholds. As a reference, the maximum allowed concentrations are about 20 μm/m³ for PM2.5 and about 50 μm/m³ for PM10.

Measurement process

Like conventional optical particle counters, the OPC-N3 measures the light scattered by individual particles carried in a sample air stream through a laser beam. These measurements are used to determine the particle size (related to the intensity of light scattered via a calibration based on Mie scattering theory) and particle number concentration. Particle mass loading- PM2.5 or PM10, are then calculated from the particle size spectra and concentration data, assuming density and refractive index. To generate the air stream, the OPC-N3 uses only a miniature low-power fan .

The OPC-N3 classifies each particle size, at rates up to ~10,000 particle per second, adding the particle diameter to one of 24 "bins" covering the size range from ~0.35 to 40 μm. The resulting particle size histograms can be evaluated over user-defined sampling times from 1 to 30 seconds duration, the histogram data being transmitted along with other diagnostic and environmental data (air temperature and air humidity). When the histogram is read, the variables in the library are updated automatically. See the "Library" section to know how to manage and read this sensor.

You can find a complete example code for reading the Particle Matter Sensor in the following link:

GP v30 04: Particle Matter SensorGP v30 04 – Particle Matter Sensor

Design and connections

The different connectors used for the sensors connection can be used for the integration of different sensors to those previously planned, provided that the organization of the pins is followed, as well as the defined electrical specifications in the Waspmote manual. In this sense, two types of different sensors are available:

Firstly, the central socket has been reserved to connect a BME280 sensor (Temperature, Humidity and Pressure Sensor), ultrasonic sensor or luminosity sensor.

Next the rest of the connectors used for gas sensors are described.