Working principle of capacitive sensors
Capacitive sensors, also known as capacitive level gauges, operate on the principle of a cylindrical capacitor. The capacitor consists of two insulated, coaxial cylindrical plates with inner and outer electrodes. When an electrolyte with a dielectric constant ε is filled between the two cylinders, the capacitance between them is given by the formula: L = (D/e) * C * D * D * e ...
Capacitive sensors use various types of capacitors as sensing elements. Because a precisely measured change will cause a change in the capacitor's capacitance, this change in capacitance can be converted into an electrical signal output by a precise measurement circuit. By measuring the magnitude of this electrical signal, the magnitude of the precisely measured quantity can be determined. This is the main working principle of capacitive sensors.
What are the advantages of capacitive sensors?
1. Good temperature reliability
The capacitance value of capacitive sensors is usually independent of the electrode material, which is advantageous for selecting materials with low temperature coefficients. Furthermore, because they generate very little heat, their reliability is minimally affected. In contrast, resistive sensors suffer from copper losses and are prone to overheating, leading to zero drift.
2. Good dynamic response
Capacitive sensors require minimal energy due to the very small electrostatic attraction between the electrode plates (approximately a few 10^(-5) N). Furthermore, because their moving parts can be made very small and thin, resulting in low mass, they exhibit high natural frequencies and short dynamic response times, enabling operation at frequencies in the megahertz range. This makes them particularly suitable for precise dynamic measurements. Additionally, their low dielectric loss allows for higher frequency power supply, resulting in high system output power. They can be used to accurately measure rapidly changing parameters.
3. Simple structure
Capacitive sensors have a simple structure, are easy to manufacture and ensure high accuracy, and can be made very small to perform certain special precision measurements; they can work in harsh environments such as high temperature, strong radiation and strong magnetic field, and can withstand large temperature changes, high pressure, high impact and overload; they can accurately measure ultra-high temperature and low pressure difference, and can also accurately measure magnetic work.
4. It can also perform non-contact measurements and has high sensitivity.
It can measure the vibration or eccentricity of rotating shafts, the radial clearance of small ball bearings, etc., without contact. When non-contact measurement is selected, capacitive sensors have an averaging effect and can also reduce the influence of workpiece surface roughness on accurate measurement.
The above is an introduction to the working principle of capacitive sensors. Having read this, you should now understand the operating mechanism of capacitive sensors. Capacitive sensors have a simple structure, good temperature stability, and are widely favored by users in the sensor market. With the rapid development of capacitive sensor technology, their market applications will continue to expand in the future.
