Gas and Humidity Sensors

A sensor is a device that detects and measures various quantities such as pressure, light, temperature, gas, and humidity as inputs and converts them into measurable data for humans or machines. But their output is usually electronic data (such as voltage or current). One of the most used types of sensors is gas sensors. A gas sensor is a device that senses the presence of gas and its concentration in the surrounding atmosphere. Based on the resistance of the sensitive material, the sensor creates a potential difference proportional to the gas concentration, which can be considered as the sensor’s output voltage. Based on the value of this voltage, the type and concentration of the gas can be recognized. The type of gas the sensor can detect depends on the sensing material inside the sensor. Another sensor widely used in industry, medicine, agriculture, the environment, and homes is the humidity sensor. Humidity is an effective factor in the health of living organisms and the proper functioning of industrial devices. A humidity sensor senses the amount of humidity of the air. In this chapter, we introduce gas and humidity sensors, their principles of operation, and their types.