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 O₃ concentration 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.