Self-calibration method of vacuum level measuring sensors in vacuum switching

In same coordinate system with discharge current as x-axis and vacuum level as y-axis, calibration curves of different vacuum interrupters are similar in shapes; therefore, a calibration curve for an idiographic vacuum interrupter can be obtained by shifting the general calibration curve along x-axis. Because the vacuum level measured by the manufacturer is the most accurate, its level is set as the base value. Then an increment of shift should be found: it is the x-axis difference value between the general calibration curve and the value measured when this vacuum interrupter leaves factory. After which, an idiographic calibration curve can be obtained by shifting the general calibration curve on x-axis by the increment. Thus, a self-calibration method is realized, which leads to an improvement of measurement accuracy. In this paper, the shifting of curves is realized by two kinds of methods: direct increment and curve fitting. This self-calibration method can be applied to various vacuum level measuring systems of vacuum interrupters.