A method for detecting a high pressure condition within a high voltage vacuum device includes detecting the position of a movable structure such as a bellows or flexible diaphragm. The position at high pressures can be detected optically by the interruption or reflection of light beams, or electrically by sensing contact closure or deflection via strain gauges. Electrical sensing is provided by microcircuits that are operated at high voltage device potentials, transmitting pressure information via RF or optical signals.