Capacitance Type Sensor

Capacitive sensors
The measured mechanical parameters, such as displacement, pressure into electric capacity change sensor. It is part of the sensitive with variable parameters of capacitor. The most commonly used form is composed of two parallel electrodes, electrode with air as medium capacitor ( see photo). If we ignore the edge effect, the panel capacitor capacitance for A / delta epsilon, epsilon is the dielectric in the dielectric constant, A two electrodes are covered by an effective area, delta two distance between electrodes. D, A, e three parameters in any change will cause the capacitance change, and can be used for the measurement of. Thus the capacitive sensor can be divided into pole change type, area change type, medium change type three class. Pole change type commonly used to measure the tiny displacement or as a result of force, pressure, vibration caused by polar distance changes (see capacitive pressure sensor ). Area change type commonly used for measuring angular displacement or larger displacement. Changes of media type is often used for level measurement and a variety of medium temperature, density, humidity measurement. Since the late 70's, with the development of integrated circuit technology, appeared with micro measuring instrument package with capacitive sensor. This type of sensor can make the influence of distributed capacitance is reduced, so that the inherent drawbacks are overcome. Capacitive sensor is a wide range of uses, has great development potential sensor.
Capacitance type sensor working principle
Capacitive sensors are also often referred to as capacitive material level meter, capacitance meter capacitance detection component is based on the principle of cylindrical capacitor, capacitor is formed by two insulated coaxial cylindrical plate of inner and outer electrodes formed, between the two cylinders filled with a dielectric constant e electrolyte, between two cylinders capacitance for C = 2 pi eL / lnD / D, type L two barrel overlap a portion of the length of the outer cylinder; D electrode diameter; D for inner electrode diameter; e medium dielectric constant. In actual measurement of D, D, e is basically unchanged, so the measured C can know the height of the liquid level, which is also the capacitance sensor has the advantages of convenient use, simple structure and high sensitivity, low price and other characteristics of the cause of.
The advantages and disadvantages of capacitive sensor
Capacitor sensor has the advantages of simple structure, low price, high sensitivity, strong overload capacity, good dynamic response characteristic of high temperature, radiation, and the strong vibration and other harsh conditions adaptability. Drawback is that output is nonlinear, the parasitic capacitance and the distributed capacitance on the sensitivity and accuracy of the impact is bigger, and the connecting circuit is complex.