Calibrated Air Quality Sensors for Smart Cities

Libelium released a particulates Gases PRO Sensor Board in May 2015. This platform features precision sensors to enable the implementation of urban monitoring, air quality, industrial, environmental or farming projects with high requirements in terms of accuracy, reliability, and measurement range. The new gas sensors line is available for both Waspmote OEM and Plug & Sense!. Two different Sensor Boards are available to monitor and measure gas levels: Gases Sensor Board (Gases) and Gases PRO Sensor Board (Gases PRO).

Gases PRO Sensor Board for Waspmote OEM

Comparative Gases and Gases PRO Sensor Boards:

A number of sensors: Gases PRO integrates 16 different gas sensors. The original Gases board integrates 12. See the complete list of parameters in the tables below.
Increased accuracy: Gases PRO measures exact values of gas concentration in ppms. The Gases board shows a range of concentration low / medium / high. Details of the accuracy ranges figure in the tables below.
Precision sensors: A sensitive new particulate matter sensor—commonly known as dust sensor—is included in the Gases PRO board. This sensor allows the measurement of PM1, PM2.5, and PM10 particles and comes calibrated from the factory.

Should I choose Gases, Gases PRO, or the New Air Quality Station?

Libelium has created different systems in terms of accuracy and pricing:

First, the last IoT product we have launched into the market is the new Air Quality Monitoring Station

In terms of accuracy, this is probably the best IoT product developed in the Air market for cities and industries. The coefficient of determination (R²) measures a comparison between an air quality device and another taken as a reference. You can discover the test & results obtained during the installations where the Air Quality Station has been developed.

The customer should consider particulates Gases PRO if she needs maximum performance sensors for metering that require accurate ppm or percentage. If the project just needs to detect gas presence or gas levels, the standard Gases Sensor Board is sufficient.

The new Gases PRO Sensor Board can read up to 16 gas sensors; it also has a high-end sensor for three parameters: temperature, humidity and pressure.

Gases PRO [New Version]
Parameter	Range	Accuracy *
Temperature	-40 to +85 ºC	Calibrated ±1 ºC (±0.5 ºC at 25 ºC)
Humidity	0 to 100% HR	Calibrated ±3% RH (at 25 ºC, range 20 ~ 80% RH)
Pressure	30 to 110 kPa	Calibrated ±0.1 kPa (range 0 ~ 65 ºC)
Carbon Monoxide for high concentrations CO	0 to 500 ppm	Calibrated ±1 ppm
Carbon Monoxide for low concentrations CO	0 to 25 ppm	Calibrated ±0.1 ppm
Carbon Dioxide CO₂	0 to 5000 ppm	Calibrated ±50 ppm (range 0~2500 ppm) ±200 ppm (range 2500~5000 ppm)
Molecular Oxygen O₂	0 to 30%	Calibrated ±0.1%
Ozone O₃	0 to 18 ppm	Calibrated ±0.2 ppm
Nitric Oxide for low concentrations NO	0 to 20 ppm	Calibrated ±0.2 ppm
Nitric Dioxide high accuracy NO₂	0 to 20 ppm	Calibrated ±0.1 ppm
Sulfur Dioxide high accuracy SO₂	0 to 20 ppm	Calibrated ±0.1 ppm
Ammonia for low concentrations NH₃	0 to 100 ppm	Calibrated ±0.5 ppm
Ammonia for high concentrations NH₃	0 to 500 ppm	Calibrated ±3 ppm
Methane and other combustible gases CH₄	0 to 100 % / LEL	Calibrated ±0.15 % LEL
Molecular Hydrogen H₂	0 to 1000	Calibrated ±10 ppm
Hydrogen Sulfide H₂S	0 to 100 ppm	Calibrated ±0.1 ppm
Hydrogen Chloride HCl	0 to 50 ppm	Calibrated ±1 ppm
Hydrogen Cyanide HCN	0 to 50 ppm	Calibrated ±0.2 ppm
Phosphine PH₃	0 to 20 ppm	Calibrated ±0.1 ppm
Ethylene Oxide ETO	0 to 100 ppm	Calibrated ±1 ppm
Chlorine Cl₂	0 to 50 ppm	Calibrated ±0.1 ppm
Particle Matter – Dust	0.5 to 16 μm (16 steps) (includes PM1, PM2.5 and PM10)	Calibrated

* Accuracy values have been calculated at average conditions: 20ºC / 101300 Pa. Accuracy levels may differ with different temperature and pressure levels, aging and in presence of third type of gases which cause cross sensitivity. See each Gas Sensor documentation for more information.

Gases v2.0 [Old Version]
Parameter	Range	Accuracy *
Temperature	40 to +125 ºC	Not calibrated ±2 ºC (range 0 ~ 70 ºC), ±4 ºC (range -40 ~ 125 ºC)
Humidity	0 to 100% HR	Not calibrated <±4% RH (at 25 ºC, range 30 ~ 80% RH), <±6% RH (range 0 ~ 100% RH)
Pressure	15 to 115 kPa	Not calibrated <±1.5% V (range 0 ~ 85 ºC)
Carbon Monoxide CO	30 to 1000 ppm	Not calibrated
Carbon Dioxide CO₂	350 to 10000 ppm	Not calibrated
Molecular Oxygen O₂	0 to 30%	Not calibrated
Ozone O₃	0.010 to 1 ppm	Not calibrated
Nitric Dioxide NO₂	0.05 to 5 ppm	Not calibrated
Ammonia NH₃	10 to 100 ppm	Not calibrated
Methane and other combustible gases CH₄	500 to 10000 ppm	Not calibrated
Molecular Hydrogen H₂	500 to 10000 ppm	Not calibrated
Hydrogen Sulfide H₂S	0.1 to 3 ppm	Not calibrated
Isobutane C₄H₁₀	50 to 5000 ppm	Not calibrated
Ethanol CH₃CH₂OH	1 to 30 ppm 50 to 5000 ppm	Not calibrated
Toluene C₆H₅CH₃	1 to 30 ppm	Not calibrated
Volatile Organic Compounds	30 to 400 ppm	Not calibrated
Hydrocarbons	–	Not calibrated

How are the Gases PRO sensors calibrated?

All the Gases PRO sensors are linear, so they behave according to a simple line like y = f(x) = m·x + c. On the other hand, the Gases Sensor Board sensors show a logarithmic response, which is harder to handle. All the gas sensors for Gases PRO are calibrated by the sensor manufacturers, in laboratories. To obtain maximum accuracy, a two-point calibration process is performed on controlled concentrations of gas in vacuum chambers. Due to the linear nature of the sensors, these two points are enough to correct the two possible drifts in m (slope) and c (constant offset). Our sensor manufacturers provide a calibration certificate for each individual sensor, with two calibration parameters. Libelium stores these parameters in an EEPROM, a non-volatile memory chip inside each gas sensor. When the user performs a sensor reading, the software system designed by Libelium reads the sensor signal and the two parameters. These three values are processed by the system, and a temperature compensation calculation is applied. From this data we obtain the concentration value in ppms – the value we want to measure. The new Temperature, Humidity and Pressure sensor for Gases PRO is calibrated in the factory. It comes with three calibration points for temperature, six points for humidity and nine points for pressure. These three parameters are automatically inter-compensated to obtain extreme accuracy.

Plug & Sense! Smart Environment PRO including new Gases PRO Sensor Board

Gases PRO Sensor Board is included in Libelium’s new Smart Cities sensing solution, Plug & Sense! Smart Environment PRO. This board also allows obtaining information about particle size and density ranging from 1um to 10um (PM1 / PM2.5 / PM10) in its surroundings, using the new particulate matter sensor—commonly known as dust sensor. For more Technical information go to Waspmote and Plug & Sense! website, and to the Gases PRO Sensor Board. If you are interested in purchase information please contact the Libelium Commercial Department.