New method for measuring dynamic pressure

Dynamic measurements and dynamic calibration are fields with great potential. Most measurements of mechanical processes take place under dynamic conditions. This works well if the measuring instrument is faster than the process to be measured. However, when the speed of the process increases the demands on the performance of the measuring instrument also increases.

Currently, calibration of mechanical measuring systems takes place under static or quasi-static conditions. Primary methods for dynamic calibration are lacking, which means that one cannot be sure what measured values in fast mechanical processes really correspond to, and that results cannot be guaranteed to be comparable.

Developing the traceability chain for dynamic pressure

At the National Laboratory for Pressure and Vacuum, we work to develop and establish the traceability chain for dynamic pressure. We have developed a shock tube which is our candidate primary standard for dynamic pressure calibration. The shock tube can realize dynamic pressure at high frequency, from 0.5 kHz to over 500 kHz. In shock tubes, the reference pressure is calculated using a theoretical model describing shock wave propagation in gases. By using alternative methods this model can be verified which strengthens its validity.

The project will develop a standard for measuring dynamic pressure by using a method called optical absorption spectroscopy. The method is based on measurement of quantum mechanical properties of the pressurized gas molecules. By measuring the linewidth and intensity of vibrational/rotational transitions, we can accurately calculate the gas pressure and temperature simultaneously. The method is insensitive to ambient disturbances and can become a strong standard for dynamic pressure measurement. In addition to verifying the shock wave model, this new standard can be used in areas not covered by the shock tube.

Validating the concept and the theoretical model

Our aim is to validate the concept of optical absorption spectroscopy for dynamic pressure measurement to establish traceable measurements of dynamic pressure.

The results will also be used to validate the existing theoretical model of the shock tube currently used to assess the reference pressure under dynamic conditions. A more reliable model can minimize measurement uncertainties and ensure accurate dynamic pressure calibration.

Important in many industries

The project contributes to better calibration of dynamic pressure, which is of great importance in many areas, such as in healthcare (blood pressure, dialysis, diagnostics), process control and energy efficiency in vehicles.