Ozone 2 click is an Ozone detection (O3) sensor, based on the MQ131 gas sensor. This gas sensor has a sensitive layer made of SnO2, which changes its resistance when exposed to ozone. The sensor is able to sense O3concentration in the range of 10 ppm to 1000 ppm. The Click board™ is also equipped with a trimmer potentiometer, used to adjust the sensitivity and offset of the MQ131 sensor. Low cross-influence of other oxidation gases such as CL2 and NO2, ensures a good accuracy of the sensor. The analog output of the sensor is sampled by a high-resolution 22-bit A/D converter (ADC), which offers the conversion result on the SPI interface. The analog signal from the sensor is also available, allowing an external ADC to be used.