I to P converter (From Emerson) is also called as “current to pressure” converter or I/P Transducer or Electro-pneumatic Converter which converts an electronic signal (analog output), typically from a control system such as PLC or DCS, to a pneumatic signal used to control a valve. This signal from the control system is typically analog signals in the range of 4mA to 20mA loop. These signals are not compatible with control valves outfitted with pneumatic actuators. Since to operate a control valve, a controlled air supply is provided to actuator via ‘converter’ which receives standard analog output (4 to 20)mA command from controller and convert proportionally in to standard pressure usually between (3 to 15)PSIG, which in turn proportionally controls the opening or closing of a valve.
Principle of Operation
I/P converter operation are based on ‘force balance principle’. To understand its working principle, a block diagram of I/P converter is shown as follows-
