The effects of temperature gradient on transient behavior of low-range differential air pressure calibration setup

Low range differential air pressure sensors are used widely in various applications. In this paper the effects of temperature change on transient behavior of the calibration setup for differential air pressure sensors, due to temperature gradient are analyzed. A high performance reference setup utilizing ideal gas law, for differential air pressure sensors, is selected for experimental analysis. The range of the setup is +/- 320 Pa with the achievable resolution down to 0.001% of the full scale. Due to the nature of ideal gas law, the experimental setup should also exhibit a high sensitivity to the temperature gradient on mechanical structure. In order to characterize the effects of this temperature gradient on the transient state of the setup, a two stage comparative experimental study is proposed. In stage one a thermal buffer is introduced surrounding the mechanical structure of the setup and the experiments are conducted by changing the temperature to the system. In stage two the temperature is changed in the same manner, but the experiments are conducted with the original experimental setup. From the results obtained by the experiments using the thermal buffer, it is observed that the temperature change of 5 degrees C, can cause the system to stay in transient state for up to 32 hours with an error of up to 10% of full scale. Whereas, the results from the original calibration setup show that the system stays in transient state for more than 96 hours with a monotonic drift. From the comparative analysis of the experimental results we conclude that the high sensitivity calibration setup for differential air pressure sensors also have a high sensitivity to the temperature gradient. Although the thermal buffer can minimize the effects of the temperature gradient on the transient behavior of the calibration setup, the modification to the existing mechanical design is considered as more practical. Future work is proposed in order to study the thermal gradient on the mechanical structure and design a setup that is less vulnerable to it.