Generally, a capacitor sensor is one type of proximity sensor used to detect nearby objects through their electrical field effect formed through the sensor. These types of sensors have some similarities with radar in their capacity to sense conductive materials while observing through insulating materials like plastic or wood.
Generally, the initial capacitance of a capacitive sensor is between 20PF and 30pF, the distance between the plates is between 25um and 200um, and the maximum displacement should be greater than 1/10 of the distance.
The working of capacitive sensors is, it measures changes within an electrical property known as capacitance. These sensors work on the change of inductance principle. Inductive sensors are available in three types High-frequency oscillation, magnetic and Electrostatic capacity. It has a lower switching frequency.
Capacitive sensing technology is often used in various detection tasks: A capacitive sensor acts like a simple capacitor. A metal plate in the sensing face of the sensor is electrically connected to an internal oscillator circuit and the target to be sensed acts as the second plate of the capacitor.
Capacitive sensors can also detect liquids like water, oil, and paint. Some capacitive sensors can be used to detect material inside a nonmetallic container. The capacitive sensors used to do this have an adjustable sensing range. We will explain how to adjust these types of capacitive sensors with an example in just a bit.
Examples of capacitive sensors are; Human interface devices like touch pads. Sometimes, mobile phones, tablet computers, and Digital audio players use capacitive sensing touch screens like input devices. So these sensors replace mechanical buttons. A capacitance sensor includes two metal plates which are separated by a ‘d’ distance and an ‘A’ area.