Theoretical Characteristics of Surface Electric Potential Sensor with Vibrating Shutter and Its Use for Measuring

A device termed the surface electric potential sensor is described. It is used for detecting the surface electric potential of a charged dielectric film and consists of a vibrating shutter, a sensing electrode, and a preamplifier. The theoretical analysis shows that the sensor has a constant current characteristic, that its sensitivity becomes greater as its vibrating frequency becomes higher, and that the preamplifier has an input resistance which makes the sensitivity maximum. Although the calibrating method for measuring the electric potential using the sensor is not the standard one, it is now in use due to its low cost and the absence of electrical danger. Hence, the method has been compared with the compensation method known as the standard and most accurate one. It is found that more accurate measurement by the calibrating method can be performed using the concept of "correcting distance".