Model PSM-530 pressure switches are essentially designed for on‑off pressure control applications such as air compressors or water pumps to control their working between the minimum and maximum setting values. At the maximum setting value, pressure switch contacts open and stops the motor. At the minimum value, pressure switch contacts close and start the motor. A diaphragm senses the change in pressure and actuates a triple pole contact switch, which enables control of 3-phase motors.