An active high voltage divider with 20-ppm uncertainty

A voltage divider has been designed which consists of a group of solid-dielectric capacitors maintained in a temperature-controlled environment, an external compressed-gas capacitor, and special electronic circuitry. The prototype divider has been constructed and preliminary results obtained to validate the operating principle and accuracy target. The principal innovative part is a feedback amplifier, complemented with an "open-loop" voltage source controlled from the high voltage. This enables achievement of a voltage ratio that is equal to the reciprocal of the capacitance ratio to well within one ppm without encountering dynamic instability problems.