Surface charge detection probe

This paper presents a low-cost contact mode surface charge probe that consists of an integrating IC, its control electronics and a metal probe. A microcontroller is used to control the probe and to A/D convert its analog output voltage. The measured object is moved by a translation stage that consists of three linear piezoactuators which are controlled by microcontrollers. The probe is calibrated by discharging a calibration capacitor into its input. The probe is used to scan the surface of an insulating material such as paper. The scans are done in normal air pressure. Charge transfer is found to occur due to both contact and break of the contact between the metal and the insulator. It is suspected that the frictional contact between the surface and the probe tip also cause charge transfer as well as charge differences on the insulator surface. Scan results from a paper surface are presented. The minimum detectable charge with the probe is approximately 100 fC.