Performance characteristics of a broad range ionization gage tube

Abstract

Seven commercial ’’broad‐range’’ Bayard–Alpert ionization gage tubes were calibrated for N2, Ar, H2, D2, and He. Between 10−4 and 10−1 Pa N2 sensitivities varied between 3.2 and 4×10−2 Pa−1 (4.3 and 5.4 Torr−1), as low as 52% of the specified sensitivity of 8 Torr−1. Relative sensitivities of 0.16±0.016 were obtained for He, and 0.37±0.04 for H2 and D2. Sensitivities were determined at reduced emission for N2 up to 1.4 Pa and 3 Pa for Ar. Argon sensitivities increased by up to 50% over this range. Voltage dependences were determined for changes in both the filament and grid bias voltages. These data showed an inexplicable grouping of the gage tubes into two distinct groups, one with small voltage coefficient typical of Bayard–Alpert gages, the other with much larger coefficients, such as expected from conventional triode gages.