Product Properties and Uses: 1, HED4 pressure relay plunger pressure relay. The composition comprising: a housing, the plunger insertion member, the spring, the adjusting member, and a switch. Second, product technical parameters: oil temperature range: -20 to +80 degrees, the contact load - AC 250V: 3A-DC 50V, 1A or 250V, 0.2A DC and inductive load, less arc can extend the service life. Third, the principle: pressure relay is the liquid pressure to open and close electrical contacts hydraulic electrical conversion element. When the system pressure reaches the set value of the pressure relay, an electric signal, the electrical components (such as solenoid, motor, time relay, electromagnetic clutch) Action, the oil circuit pressure relief, commutation, actuator sequence of actions, or turn off the motor so that the system stops working, play a security role. Pressure relay plunger, diaphragm, spring tube and bellows-type form of four structures. Following as an introduction to the plunger pressure relay (see Figure) [1]? Working principle: When the inlet from the bottom of the relay into the liquid pressure reaches the set pressure value, push the plunger 2 Move this displacement amplified through the lever to promote micro switch action. Change the amount of compression of the spring the relay operation pressure can be adjusted. Applications: for security protection, control the order of action of the actuator for the opening and closing of the pump for the unloading of the pump. Note: Pressure relays must be placed significant change in pressure can be output electrical signals. If the pressure relay on the return line, the return oil directly back to the tank, the pressure does not change, so the pressure relay will not work.