ABSTRACT
The induced electrical current depends on the ionization processes that are related to the reduced electric field, geometrical electrode configuration, magnetic field, molecular density, and thus pressure. At a smaller electric field, electric discharge can be triggered and maintained only with auxiliary agents such as thermionic electrons, alpha particles, energetic photons, or gamma radiation. The simplest electric discharge gauges are glow discharge tubes. The discharge tube comprises just two plate electrodes with about 1000 V across the electrodes. Discharge pressure gauges with optical sensing are contactless methods of pressure measurement that can be based on inducing a radio frequency electric discharge at low pressures and sensing optical emission of the electric discharge. Recording the optical emission can be performed by a photosensitive element, processing photoelectric signal, and its amplification and measurement. Pressure gauges based on D.C. cold electric discharges in combination with magnetic fields were introduced to vacuum technique by Penning in a Philips Company.
