Pressure balance elastic distortion
We have been studying the behaviour of pressure balances at high pressure. In particular we are interested in analysing how the area of a piston-cylinder unit changes with increasing pressure. Our knowledge of this change in area with pressure, often called elastic distortion, is the limiting uncertainty term when establishing our high pressure standards. We have developed a method to predict the change in area of a pressure balance and are currently carrying out measurements on a specially constructed pressure balance to confirm the theoretical predictions.
Generation of small absolute and differential pressures
We have been developing techniques to generate small absolute and differential pressures, using gas operated pressure balances. We have a twin pressure balance facility that can be used to generate differential pressures in the range 1 to 9000 Pa, with a standard uncertainty of 4 mPa + 1.4 ´ 10-5 p . We are currently developing a pressure balance method to generate absolute pressures in the range 10 to 10000 Pa.