To provide a method for estimating the vacuum leakage and electric circuit defect of a strain gauge type pressure sensor being employed as a vacuum sensor accurately in safety without utilizing radioactivity and without causing any pollution over a wide range of discharge and electric output characteristics.
Upon elapse of about 10 days after manufacture of a sensor, a DC 600V voltage is applied between a metal case 6 and the terminal where all electrodes 2 are short-circuited. If a discharge current flows, it means vacuum leakage at a rate higher than maximum allowable rate and thereby the sensor is rejected otherwise a DC 6V voltage is applied to the electrode 2 and the output voltage is recorded. Upon elapse of another 10 days, output voltage is measured and if the voltage difference is higher than several mV, a decision is made that the maximum allowable vacuum leakage rate is exceeded and the sensor is rejected.
IRISA ATSUO
MATSUI TOMIO
