Adjustable pressure-operated switch - has piezoelectric bridge-type pressure transducer connected to monitored pressure line and differential amplifier

摘要

The adjustable pressure-operated switch for hydraulic or pneumatic equipment comprises a piezo-electric bridge type pressure transducer connected to a pressure line being monitored. The output from the transducer, a variable voltage, is taken to one input of a differential amplifier via a lay contact. Another input to the differential amplifier is fed with a reference voltage set on a potentiometer which is proportional to the desired pressure in the system. The differential circuit operates a second relay contact to control a feed pump motor. The upper and lower pressure limits (pressure differences) are set on a further potentiometer whose output is fed to a summer. The summer is connected to the transducer's output and to one of the change-over contacts on the input to the differential amplifier.