Advantages and disadvantages of capacitive sensors – Turck

Advantages of capacitive sensors

1. Good temperature stability

The capacitance value of capacitive sensors is generally independent of the electrode data, which is conducive to the selection of data with low temperature coefficient, and has little impact on stability due to its own small heat generation. The resistance sensor has copper loss, which is easy to heat up and cause zero drift.

2. The structure is simple

The capacitive sensor has a simple structure, is easy to make and ensures high accuracy, and can be made very delicate to achieve some special measurements; It 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, overload, etc.; It can measure the ultra-high temperature and low pressure difference, and can also measure the magnetic work.

3. Good dynamic response

Because the electrostatic attraction between the electrode plates is very small (about a few 10^(-5)N), the capacitive sensor requires very little effect energy, and because its movable part can be made very small and thin, that is, the mass is very light, so its natural frequency is very high, the dynamic response time is short, and it can work at a frequency of several megahertz, which is especially suitable for dynamic measurement. And because of its low dielectric loss, it can be powered with a higher frequency, so the system works at a high frequency. It can be used to measure parameters that change at high speed.

4. It can be measured non-touch and has a high degree of activity

The oscillation or eccentricity of the rotary shaft and the radial clearance of small ball bearings can be measured without touch. When non-touch measurement is selected, the capacitive sensor has an average effect, which can reduce the influence of the surface roughness of the workpiece on the measurement.

In addition to the above-mentioned advantages, capacitive sensors can measure extremely low pressure, force, and small acceleration and displacement because of the small electrostatic attraction between the electrode plates, and the input force and energy required are very small, so they can be very active, have high resolution, and can sense a displacement of 0.01 μm or even smaller. Because of its small loss of air and other media, the zero residual value that occurs when the differential structure is selected and connected to the bridge type is small, so the circuit is promised to be amplified at a high rate, so that the instrument has a high degree of activity.

Advantages and disadvantages of capacitive sensors – Turck

Advantages and disadvantages of capacitive sensors – Turck

Capacitive sensor defects

1. The output impedance is high and the load capacity is poor.

No matter what type of capacitive sensor, the capacitance is very small, generally tens to hundreds of picometers (pF), so the output impedance of the capacitive sensor is very high, up to Ω. Because the output impedance is very high, the output power is small, the load capacity is poor, and it is easy to be affected by external interference and instability, and even cannot work in serious cases.

2. Parasitic capacitance has a great impact.

Capacitive sensors have a small initial capacitance, but large parasitic capacitances such as the lead cable capacitance that connects the sensor to the electronic circuit, the stray capacitance of the electronic circuit, and the capacitance of the capacitor plate and the surrounding conductors. The presence of parasitic capacitance not only reduces the measurement activity, but also causes a nonlinear output. Because the parasitic capacitance is randomly changed. Therefore, the sensor is in an unstable working condition. Affects the accuracy of the measurement.

Advantages and disadvantages of capacitive sensors – Turck

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