A study on the pressure gradient effect due to a leak in a pressure calibration system

Abstract

Leaks in a pressure calibration system should be as small as possible in order to reduce the pressure difference between the pressure standard and the device under test (DUT). However, a pressure calibration system that is perfectly sealed from the external environment does not exist, and a pressure difference due to leakage can affect the calibration results. This type of effect should be evaluated precisely because DUTs, such as precise digital pressure gauges with resolutions of less than 1 part in 106, are used widely in industry and the pressure difference due to the leak effect is expected to be larger than the resolution of the DUTs. In addition, precise digital pressure gauges for intercomparisons have been used as transfer standards to determine the degree of equivalence of pressure measurement standards among national measurement institutes (NMIs). This paper explores the leak effect using a leak control valve when a precise digital pressure gauge is calibrated using a pressure balance up to 100 kPa in an absolute mode. Experiments were performed according to an applied pressure, leak amount, tube length and pressure media. It is concluded that the uncertainty caused by a possible leak should be included in the uncertainty evaluation of the calibration results.