Measurement of the latency of dynamic pressure sensors

Dynamic pressure measurement is of great importance in several applications. Despite that, knowledge of how measurement systems behave in very fast processes is limited. Calibration of pressure measurement systems is traditionally done under static conditions. The development of the shock tube aims to produce a primary standard for dynamic calibration of pressure measurement systems used in dynamic applications.

Latency importance  

Information about the latency (time difference between the output and input signals) of pressure measurement systems is crucial in many industrial applications. For example, in the internal combustion engine where the in-cylinder pressure is measured with the crank angle, the latency of the pressure measurement system can produce phase shift that results in significant errors in the measurements.

Latency measurement

To measure the latency of the device under test (DUT), the shock tube was equipped with an optical sensor based on shadowgraphy. The optical sensor has a response time in nanosecond time scale which is several orders of magnitude faster compared to the response of the pressure measurement systems. Therefore, it was used as a reference to detect the time of shock front impingement on the DUT from which its latency was estimated. By the knowledge of the DUT latency, its phase response versus frequency was calculated. 

Results

After the project, a robust method provides traceable measurement of the latency of the pressure measurement systems was developed and accurate phase determination was achieved. The project results were published in the scientific journal Metrologia.