Dynamic operation of a micro-thermocouple sensor as a vacuum gauge

We present an experimental characterization of a new vacuum gauge based on a K type micro thermocouple with 25.4 mu m diameter. This sensor is intended for the simultaneous measurement of the temperature and pressure in the ranges extending from 293 K to 400 K and 10(-1) Pa to 10(5) Pa respectively. The paper gives an investigation of the micro-thermocouple vacuum gauge signal for the oscillating heating and cooling processes. The operation of the sensor is based on the analysis of the frequency of the oscillating signal obtained from an electric Joule heating of fixed duration and a cooling of variable duration depending on gas pressure in the vacuum chamber volume. The frequency of the signal oscillation is a function of the gas pressure in the system. Due to its low thermal inertia (time constant of 30 ms), this gauge gives two pieces of information simultaneously: the temperature and the pressure of the gas. Experiments are conducted with dry air. (c) 2013 Elsevier Ltd. All rights reserved.