Capacitive Thickness Gauges and Displacement Gauges: Frequently Asked Questions

Capacitive thickness and displacement gauge systems measure the capacitance between the sensor and the object being measured, and then calculate the distance.

Capacitance refers to the ability to store electric charge between insulated conductors. The VE series gap detector, a capacitive displacement sensor, has the same structure as a capacitor.

The diagram below illustrates a sensor and an object to be measured. The sensor and the object are electrically connected and placed facing each other. This creates capacitance between the sensor and the object, and this capacitance can be expressed by the equation in the diagram on the right. In this equation, the dielectric constant of air (ε) and the electrode area of the sensor (S) do not change and are therefore fixed values. On the other hand, it can be seen that the capacitance (C) changes when the distance (D) between the sensor and the object to be measured changes. Therefore, conversely, by measuring the capacitance (C), the distance (D) between the sensor and the object to be measured can be determined.

Capacitive displacement gauges utilize this principle to measure the distance between the sensor and the object being measured. Since electricity must flow to measure capacitance, the sensor, the object being measured, and the measuring instrument must be electrically connected. If this is neglected or not properly connected, noise may be introduced, the measurement values may become unstable, and measurement errors may increase. Therefore, always remember to ensure continuity.