4-20ma Modulating Type Electric Actuator Ball Valve, Valve Size: 3 inch

On/Off Ball Valves On/Off electric actuated valves switch from completely open to completely closed without stopping anywhere in between. Once the valve is completely cycled fully open or closed the motor is switched off by internal cams striking limit switches. For example, when a "close" signal is received, the motor is energized and begins rotating. As the motor closes the valve an integral cam turns on an internal shaft. Limit switches ride on this cam until the cam lobe causes the limit switch to break the circuit and shut off the motor. The reverse is true for opening the actuator valve. Positioning Valves Some applications require an actuator valve to open partially or react to varying flow conditions. For electrically actuated valves, this is accomplished by a digital position sensor. An external control signal (such as 4-20mA or 0-10V) is generated based on flow requirements. A microprocessor in the actuator continuously compares the analog input signals to the physical position via an output feedback system, moving the actuator as required to balance the signals and find the desired position. In most cases the low end of the signal range (4mA or 0V) is used to close the valve. This is called "normally closed" operation. Some applications might require the valve to be normally open in which case either the signal limits or the valve mounting would be reversed.