Primary Sinusoidal Calibration of Pressure Transducers

Abstract

Pressure transducers are frequently used in dynamic environments such as combustion engines, aerospace applications or industrial process control. Like for every measurement task it is essential to know the uncertainty of the obtained measurement result, even in a dynamic environment. Therefore it is remarkable that there is no traceable standardized method to quantify the frequency response of a pressure transducer. Due to this lack of investigation methods the authors have made an effort to develop a primary method to calibrate pressure transducers dynamically. This method allows to measure the frequency response with sufficient pressure amplitudes up to 1 MPa in a frequency range up to 10 kHz. In the paper the pistonphone based apparatus is presented. This pressure generator compresses a liquid by a piston. The fundamental idea is to determine the pressure rise of the employed fluid primarily by measuring the movement of the piston. Therefore the mass balance is applied to the device and leads to Ṗ=KA Ẋ/V0 Where Ṗ is the dynamic pressure, K is the bulk modulus, A is the area of the piston, V0 is the initial volume of the fluid and Ẋ is the velocity of the piston. The frequency response of the transducer is then calculated by (f)=U(f) Ṗ(f)Where U(f) is the frequency dependent output of the transducer. Besides a detailed discussion of the apparatus, the paper includes the investigation of the measurement uncertainty. Namely the uncertainty contribution of the piston area A, the initial volume V0 and the deviation between an iso-thermal bulk modulus K at low frequencies and the adiabatic bulk modulus at higher frequencies. Furthermore first measurement results will be presented, which confirm the test setup and the primary approach to measuring the frequency response.