High-Resolution Micro-Pirani Pressure Sensor With Transient Response Processing and Time-Constant Evaluation

A micro-Pirani pressure sensor, which consists of a pressure-dependent thermoresistance gauge, is traditionally exploited using a steady-state resistance measurement. Any signal variation occurs over an offset voltage due to the imperfection of the device, which affects the sensor's sensitivity. This paper presents, for the first time, an experimental investigation of a micro-Pirani gauge based on its dynamic behavior when heated by a current step. Such processing magnifies the pressure dependence of the gauge's signal by eliminating the constant offset influences on the measurement. Furthermore, a first-order low-pass filter step response identification of the experimental transient signal strongly reduces the noise influence on the measurement. Furthermore, such identification enables a direct calculation of the time constant. This paper investigates the pressure measurement based on the time-constant evaluation, which provides a range of measurement and a maximal sensitivity significantly shifted toward the atmospheric pressure compared to that of a traditionally processed Pirani gauge. The heating step, the recording of the transient response signal, and its digital postprocessing can be easily achieved by a small-sized controller. The proposed system provides a substantial performance enhancement of the micro-Pirani pressure sensor.