Capacitive sensors use various types of capacitors as sensing elements because the changes in accurate measurement will lead to changes in the capacitance of the capacitors. According to the precise measurement circuit, the changes in capacitance can be converted into electrical signal output.
The measured element in capacitive sensing applications is a capacitor formed between a sensor pad (an area of conductive material) and surrounding conductive material, which is typically a ground fill of some density and distance. The capacitance value of a sensor is given by:
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.
There are four basic elements in the capacitive sensor structure, namely sensor plate, oscillator, trigger circuit, and an output terminal. The target object and sensor board form the oscillator feedback circuit.
A basic capacitive sensor is anything metal or a conductor and detects anything that is conductive or has a dielectric constant different from air. Figure 2-1 displays three basic implementations for capacitive sensing: proximity/gesture recognition, liquid level sensing, and material analysis.
In the actual measurement, D, d, and e are basically unchanged, so the level of the liquid can be known by measuring C, which is also one of the reasons that the capacitive sensor has the characteristics of convenient use, simple structure, high sensitivity, and low price. Capacitive sensors use various types of capacitors as sensing elements.