A traceable dynamic calibration research of the measurement system based on quasi-static and dynamic calibration for accurate blast overpressure measurement

Abstract

To ensure measurement accuracy in blast tests, the blast overpressure measurement system with piezoelectric sensors needs to be calibrated. Due to the charge leakage on the piezoelectric crystal and the decrease in the service life of the piezoelectric sensor under static pressure loads, the static calibration is not suitable here. This paper presents a traceable dynamic calibration method combining the quasi-static calibration using a drop-weight device and the dynamic calibration using a shock tube. First, the normalized low-frequency and high-frequency characteristics of the measurement system can be derived by the quasi-static calibration and the dynamic calibration, respectively. Then, based on the quasi-static calibration, a calculation method is proposed to obtain the performance characteristics which can be traceable to the SI, including the sensitivity, the linearity and the repeatability of the measurement system. Therefore, this calibration method combining quasi-static and dynamic calibration can help to obtain the frequency characteristics and the performance characteristics of the measurement system with traceability. For accurate blast overpressure measurement, based on the frequency characteristics derived from the calibration, the dynamic modelling and compensation are implemented on the measurement system to make the compensated measurement system meet the so-called undistorted measurement requirements. As the measurement system is compensated, it can be proved that the performance characteristics calculated by the quasi-static calibration are consistent with that of the compensated measurement system. So, the blast overpressure can be accurately represented with the multiplication of the calculated sensitivity traceable to the SI and the output voltage of the measurement system in blast overpressure measurement. By combining the traceable dynamic calibration with dynamic modelling and compensation, the calibrated and compensated measurement system can realize accurate blast overpressure measurement. Finally, influence factors of the blast overpressure measurement uncertainty are analyzed and possible measures to further improve the measurement accuracy are illustrated.