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what is the basic working principle of I/P and Positioner in
any control valve.

Question Posted / m m chotrani

Answer Posted / m m chotrani

It works on force balance principle. A coil is suspended
in a magnetic field on a flexible mount. At the lower end
of the coil is a flapper valve that operates against a
precision ground nozzle to create a backpressure on the
servo diaphragm of a booster relay. The input current flows
in the coil and produces a force between the coil and the
flapper valve, which controls the servo pressure and the
output pressure.Zero adjustment of the unit is made by
turning a screw that regulates the distance between the
flapper valve and the air nozzle. Span adjustmentis made by
varying a potentiometer,which shunts input current past the
coil.

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