Why is an I/P (current-to-presssure) & a P/I (pressure-to-current) transducer in a process control system??

You may use an example in your explanation. Internet sources prefered. thanksWhy is an I/P (current-to-presssure) %26amp; a P/I (pressure-to-current) transducer in a process control system??
I/P transducers, are used to control pneumatically actuated control valves, either manually or by a PID (Proportional-Integral Derivative) controller, discrete or part of a central control system. IOW, an input current, normally 4 to 20 mA, controls the air pressure, which is applied to the control valve actuator. Control air pressure normally ranges between 0 to 30 PSIG.





P/I or ';pressure-to-current'; transducers, translate process pressure, such as steam, or other fluids, into 4-20 ma current values, to be inputed remotely into a single instrument or a control system interface point.Why is an I/P (current-to-presssure) %26amp; a P/I (pressure-to-current) transducer in a process control system??
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