Thermionic ionisation-type pressure gauge - provides wide-range pressure measurements through use of additional grid structure

摘要

The pressure gauge consists of a thermionic tube with flat anode (1) and ion collector (2) in plat form. Parallel to these elements is a flat grid (3) placed roughly midway between the collector and the cathode (4). The latter is directly-heated iridium wire coated with thorium oxide. Th current which can be measured in the collector and the grid can, in the measurement of higher pressures, be combined according to a known relationship and with the aid of e.g. a process computer, a linear relationship between the pressure and the total current well above the pressure range, which could otherwise be expected at the peak of the ionisation current-pressure characteristic, can be obtd. This relationship is obtainable above 1 Torr. The pressure gauge construction is suitable for use in vacuum processes operating within the pressure range 10 Torr to 10-6 Torr.