Investigation on the thin film pirani vacuum sensor using a constant voltage drive-mode diode-heater

Abstract

A thin film Pirani vacuum sensor having a single micro-heater and two diode temperature sensors composed of pn junction diodes on the sensing cantilever, fabricated by micromachining technologies, is driven by a constant applied voltage driving mode using the diode heater to enhance the pressure sensitivity. In these experiments new diode-sensors are used as a temperature sensor, which has a proportional output signal voltage ΔV to the absolute temperature T as ΔV=α T. These new type diode-sensors are useful to measure the temperature difference ΔT between these diode sensors. In this pressure sensing the null detection method is adopted for accurate measurements. In the low pressure range such as 1 × 10 -3 - 1 × 10 0 Pa the diode-thermistor will be useful because of its higher temperature sensitivity. It is demonstrated that this thin film Pirani vacuum sensor can measure the wide pressure range of 1 × 10 -3 to 1 × 10 5 Pa, which is about 2 order wider pressure range than that of usual Pirani gauge. © 2008 The Institute of Electrical Engineers of Japan.