A closed‐loop tracking circuit incorporating high‐impedance metal–oxide–semiconductor (MOSFET) transistors has been developed for measuring high‐voltage electrostatic fields on the surfaces of conducting electrodes. One MOSFET is used as a field sensor, and the other as a tracking ‘‘dummy.’’ The feedback circuit yields a signal voltage output that is at the same time linearly dependent on the external surface field being measured, and virtually independent of the gain and the offset parameters of the specific MOSFET device used as a sensor.