A Theoretical and Experimental Study of an Unsteady Pressure Measuring System

Experiments were performed to determine the frequency response of gas filled instrument tubes, and the results were correlated with a theoretical model. The theoretical model developed by Bergh and Tijdeman for a series connection of thin circular tubes and volumes was studied in full detail and employed. A measuring system was designed and built to measure pressure ratio and phase lag employing thin nylon or vinyl tubes and strain gage transducers. 1'leasurements were performed using cathode ray tube, strip chart, analog techniques and also a commercial electronic function analyzer and the various results were compared. The theoretical and experimental influence of different parameters was observed. Dynamic response of the tubes with a terminal cavity was obtained at atmospheric and vacuum static pressure, using air and/or Freon-12 as different filling gases and with and without a terminal, multi-port scanner valve. The theory and experiments displayed the same qualitative dynamic pressure response. Finally an at. tempt was made to develop the theoretical model for a step input pressure disturbance for a series connection of thin circular tubes and volumes.