Electro pneumatic is used for controlling movement of final control element such as Linear Cylinder, Diaphragm Control valve or Rotary actuator device which accept directly variable electronic signal & E/P positioner is a precision with the help of auxiliary high pressure supply accurately controls movement of final control element corresponding to set point.
• Common unit for all type of actuators.
• Simple calibration using three keys & LCD display
• Auto start function with self adjustment of zero & span
• Selectable freely programmable characteristic
• Minimum air consumption
• Tight shut off function
• Minimum linkages to give error free feed back
• No air consumption under balance condition hence saving of energy
• Action field reversible
• Digital output indicating precise position during operation
• Unit can be modified for use with electrical actuator
Usually available in MS powder coated housing suitable for panel mounting with solenoid provided in separate weather proof housing & linear pot for field mounting. However optionally for field mounting with built in solenoid with die cased aluminium weather proof housing can be provided at extra cost.
Positioner receives mainly three inputs such as :
• 230 V a. c. 50 C/s, power supply
• 4-20 MA-Input signal (Control)
• Potentiomter- Output ( Feedback )
The microprocessor based instrument amplifier of the positioner receives variable input control signal & potentiometer output feedback signal. Microprocessor compares these values & depending upon vectorial difference decides & fires the corresponding relay which in turn triggers solenoid to admit & exhaust air from actuator. The system is based on modulation of signal & its time function. The microprocessor precisely calculates the time function & accurately positions. The movement of actuator standard instrument available with input control signal of 4-20 MA. However system can be modified for accepting other variable depending upon specific requirement. Similarly normal characteristic is linear, however optionally other characteristics such as equal percentage or square-root extraction is available Simple installation & largely automatic commissioning.