Patent ID: 8459289

Claim:
An electro-pneumatic positioner, comprising: a control output generating device calculating a deviation between a valve opening setting value sent from a higher-level device and an actual opening value that is fed back from a control valve that is subject to control, to generate, as a control signal, an electric signal in accordance with the deviation; an electro-pneumatic converting device converting a control output produced by the control output generating device into a nozzle back pressure of a nozzle/flapper mechanism that operates through air that is supplied through a fixed orifice from a pneumatic pressure supplying source; and a nozzle back pressure amplifying device for amplifying a nozzle back pressure, converted by the electro-pneumatic converting device and outputting to an operating device of the control valve as an output pneumatic pressure; wherein: a blockage location identifying device for identifying a location wherein a blockage has occurred, either the fixed orifice or the nozzle/flapper mechanism, based on a magnitude of shift and on a direction of shift of the control output generated by the control output generating device relative to the nozzle back pressure converted by the electro-pneumatic converting device.