Capacitive sensor is based on various types of capacitors as sensing elements, will be measured to change the physical or mechanical quantity into a capacitance change device, in fact, is a capacitor with variable parameters. Capacitive sensors are widely used in displacement, Angle, vibration, velocity, pressure, composition analysis, dielectric characteristics and other aspects of measurement. The most commonly used are parallel plate or cylinder capacitors. The following small series to introduce the working principle and classification of capacitive sensor

 

A capacitive sensor working principle and classification

 

The principle of

 

Capacitive sensors are often known as the capacitive material level meter, capacitive material level meter capacitance detecting element is based on the principle of the cylindrical capacitor work, capacitor consists of two insulated coaxial cylindrical plate of internal electrode and external electrode, between two tube filled with dielectric constant for epsilon electrolyte, the capacitance between the two cylinders

 

Where L is the length of the overlap part of the two cylinders; D is the diameter of the outer cylinder electrode; D is the diameter of the inner tube electrode; E is the dielectric constant of the intermediate medium. In the actual measurement, D, D, E are basically unchanged, so the level of liquid level 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 are based on various types of capacitors as sensing elements, because the measured changes will lead to capacitor capacitance changes, through the measurement circuit, the capacitance changes can be converted into electrical signal output. Measure the size of electrical signal, can judge the measured size. That's how capacitive sensors work.

 

classification

 

Capacitive sensors can be divided into three types according to the working principle of sensors: variable pole distance type, variable area type and variable medium type.

 

Capacitive sensors can be divided into three types of structure according to the structure of the sensor. They can also be divided into two kinds of linear displacement and angular displacement according to the form of displacement, and each kind of sensor plate shape is divided into flat (circular) plate shape and cylindrical (cylinder) shape, although there are other shapes such as spherical shape and zigzag shape, but generally rarely used. Among them, differential type is generally superior to single group (unilateral) type sensor, which has the characteristics of high sensitivity, wide linear range and high stability.