Production - Capacitive Sensors - Brand [Veckway]

Any two conductors can form a capacitive connection, so in addition to the capacitance between the plates, capacitive sensors may also have capacitive connections between the plates and surrounding objects (including various components in the instrument and even the human body). This additional capacitive connection is called parasitic capacitance. Parasitic capacitance causessensorChange in capacitance. Due to the small capacitance of the sensor itself, coupled with the extremely unstable parasitic capacitance, it can lead to unstable sensor characteristics and cause serious interference to the sensor.

The methods for eliminating and reducing the influence of parasitic parameters are summarized as follows.

(1) Shorten传感器The distance to the front-end of the measurement line. Applying integrated circuits and ultra small capacitors to measurement circuits, or integrating some components with sensors, can reduce parasitic capacitance values while keeping them fixed.

(2) Drive cable method. This is an equipotential shielding method, whichCircuitThe connection method ensures that the core wire of the transmission cable is equipotential with the inner shield, eliminating the capacitive leakage of the core wire to the inner shield and thus eliminating the influence of parasitic capacitance. At this point, the capacitance between the inner and outer shields becomes the load of the cable driven amplifier. Therefore, the driver amplifier is a in-phase amplifier with high input impedance, capacitive load, and amplification factor of 1.

(3) Overall shielding method. Protect the entire bridge (including the power supply and transmission cables) with a unified shielding cover. The parasitic capacitance C between the common electrode and the shield only affects the sensitivity, while the other two parasitic capacitances affect the initial balance and overall sensitivity of the bridge to a certain extent, but do not affect the normal operation of the bridge. The influence of parasitic parameters on sensor capacitance is basically eliminated.