Component - Capacitive Capacitive Sensor - Manufacturer [Weckway]

capacitorIt is one of the three major types of passive components in electronic technology (resistors, inductors, and capacitors), which uses the principle of capacitors to convert non electric quantities into capacitive quantities, thereby achieving the conversion of non electric quantities into electric quantitiesCapacitive sensor. Capacitive sensors have been widely used in the measurement of displacement, pressure, thickness, level, humidity, vibration, speed, flow rate, and component analysis. The accuracy and stability of capacitive sensors are also improving day by day, and capacitive sensors with a precision of up to 0.01% are already available in foreign markets. A 250mm measuring rangeCapacitive displacement sensorThe accuracy can reach 5 μ m. Capacitive sensors, as a type of sensor with wide frequency response, wide application, and non-contact measurement, have great potential for development.

Capacitive sensorThe main drawbacks are as follows:

1. High output impedance and poor load capacity

The capacity of capacitive sensors is limited by the geometric dimensions of their electrodes and is not easily made very large, usually ranging from tens to hundreds of microfarads, or even only a few microfarads. Therefore,Capacitive sensorThe output impedance is high, resulting in poor load capacity and susceptibility to external interference, leading to instability and even inability to work in severe cases. Proper shielding measures must be taken to avoid inconvenience in design and use. A high capacitance also requires the insulation part of the sensor to have a very high resistance value (several tens of megaohms or more), otherwise the insulation part will act as a bypass resistor and affect the performance of the instrument. Therefore, special attention should be paid to the surrounding environment such as temperature, cleanliness, etc. If high-frequency power supply is used, it can reducesensorOutput impedance, but high-frequency amplification and transmission are much more complex than low-frequency ones, and parasitic capacitance has a greater impact, making it difficult to ensure operational stability.

2. Parasitic capacitance has a significant impact

The initial capacitance of capacitive sensors is small, while the connectionsensorThe so-called parasitic capacitance of electronic circuits, such as lead capacitance (cable capacitance, 1-2m wire can reach 800pF), stray capacitance of electronic circuits, and capacitance formed by the sensor's inner plate and surrounding conductors, is relatively large. This not only reduces the sensitivity of the sensor, but also these capacitances (such as cable capacitance) often vary randomly, which will make the instrument work very unstable and affect measurement accuracy. Therefore, there are strict requirements for the selection, installation, and connection of wires. For example, using high-frequency wires with good shielding and small self distributed capacitance as leads, with thick and short leads, it is necessary to ensure that the stray capacitance of the instrument is small and stable, otherwise high measurement accuracy cannot be guaranteed.

3. Nonlinear output characteristics

Variable polar distance typeCapacitive sensorThe output characteristics of are nonlinear, and although differential methods can be used to improve them, it is impossible to completely eliminate them. Other types of capacitive sensors only exhibit linear output characteristics when the edge effect of the electric field is ignored. Otherwise, the additional capacitance generated by edge effects will directly overlap with the sensor capacitance, resulting in nonlinear output characteristics. It should be pointed out that with the rapid development of materials, processes, electronic technology, especially integrated technologyCapacitive sensorThe advantages are developed while the disadvantages are constantly overcome. Capacitive sensors are gradually becoming a highly sensitive and accurate sensor with great development prospects in dynamic, low-voltage, and some special measurement fields.