Influence of a Scanning Box on the Settling Time of Multi-Hole Pressure Probes

Abstract

The present paper presents an investigation on the settling time of a measurement setup with following components: multi-hole pressure probe, pressure scanning box, connection tubes, piezoresistive pressure transducer. First, an analytical model is presented to calculate the settling time of such a pressure measurement system. The generic model describes the response time of the pressure transducer due to a sudden jump of the pressure at the probe head. Furthermore, the model is extended to take into account the influence of the scanning box. Second, an experimental campaign is performed to verify the analytical model. For this purpose, a three-hole pressure probe is positioned in the open-jet wind tunnel at constant velocity and yaw angle, to generate large pressure differences between the individual sensing holes. Then, the pressure signals are switched by the scanning box in a sequential manner to the single pressure transducer. The results show that the extended analytical model describes the relaxation behaviour and settling time of the measurement system. The obtained time constant can be used to optimize the experimental process to reduce total measurement time. Finally, some conclusions drawn from the investigation of the sensitivity of the time constant on geometrical parameters are presented.