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.