Disadvantages of capacitive sensors
1 high output impedance, poor load capacity
Regardless of the type of capacitive sensor, the capacitance is very small, generally tens to hundreds of picofarads (pF), so the output impedance of the capacitive sensor is very high. ~ Ω. Due to the high output impedance, the output power is small, the load capacity is poor, and it is susceptible to external disturbances, which may cause instability. In severe cases, it may not work.
2 parasitic capacitance has a large impact
The initial capacitance of a capacitive sensor is small, and the parasitic capacitance of the lead cable capacitor connecting the sensor and the electronic circuit, the stray capacitance of the electronic circuit, and the capacitance formed by the capacitor plate and the surrounding conductor are large. The presence of parasitic capacitance not only reduces measurement sensitivity, but also causes nonlinear output. Because the parasitic capacitance is randomly changing. Therefore, the sensor is in an unstable working state. Affects measurement accuracy.