Precision Electroscope

This circuit can precisely measure electrostatic charge. The charge to be measured is stored on C1 (a high quality MKT capacitor with a value of 1-2 µF). The voltage (U) across the capacitor (C1) is related to its charge (Q) by the equation U = Q/C1. Operational amplifier IC2 buffers this very high impedance source. An input lead is connected to one side of capacitor C1 and terminated with a test probe. The other side is connected to an earth lead and to a convenient earth point.