| 摘要 |
PURPOSE:To prevent a differential sensor from being broken down, by providing an excessive pressure preventing mechanism, in addition to an automatic zero adjusting mechanism. CONSTITUTION:In case an excessive pressure has been applied to a high pressure chamber H, signals are generated to a microprocessor (muP) from the first pressure sensor P1 and the second pressure sensor P2, and the muP decides that the excessive pressure has been applied, from a difference of the signals of these two pressure sensors, and generates a signal for closing the first control valve Vd and opening the second control valve Vo. As a result, the pressure of the high pressure chamber H is stopped by the first control valve Vd, pressure of a low pressure chamber J is applied to a high pressure side of a differential pressure sensor Pd, through the second control valve Vo, a pressure difference goes to zero and balanced, and the differential pressure sensor is not broken down. Also, even in case an excessive pressure is applied from the low pressure chamber J, the differential pressure sensor Pd is not broken down in the same way.
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