Evaluation and correction for long-term drift of hydraulic pressure gauges monitoring stable and constant pressures

We have evaluated a long-term drift of hydraulic pressure gauges which are kept under constant pressure application. Three pressure gauges were pressurized and kept at 100 MPa, and the variations in calibration results at 100 MPa have been traced for 800 days. The calibration results significantly varied immediately after the pressure application, and the variation rate became small and almost constant as the pressure was continuously applied. The observed drift trend was different from the drift which is observed when the gauges are always kept at atmospheric pressure. In addition, during the pressure application, the pressure was intermittently released to atmospheric pressure for a short time, and outputs at atmospheric pressure were obtained. The calibration results at 100 MPa and atmospheric pressure showed a similar drift trend, showing that most part of the drift under pressure can be corrected by zero offset. Several methods are proposed to appropriately evaluate and correct the long-term drift of pressure gauges during use under constant pressure application.