I/P transducers

Once the desired control action has been transformed to an analogue signal, it is transmitted to the final control element over the transmission lines. However, the final control element s actuator may require a different type of signal and thus another transducer may be necessary. Many control valve actuators utilise a pressure signal so a current-to-pressure (I/P) transducer is used to provide a pressure signal to the actuator. 

Pneumatic signals are represented by solid hnes that are cross-hatched intermittently. The signal from the I/P transducer to the pneumatic positioning valve is pneumatic. 

Transducers The ciirrent-to-pressiire transducer (I/P transducer) is a conversion interface that accepts a standard 4-20 rnA input current from the process controller and converts it to a pneumatic output in a standard pneumatic pressure range (normally (),2-L0 bar [3-15 psig] or, less frequently, 0,4-2,0 bar [6-30 p.sig]). The output pressure generated by the transducer is connected directly to the pressure connection on a spring-opposed diaphragm actuator or to the input of a pneumatic valve positioner. 

Figure H-7 is the schematic of a basic I/P transducer. The transducer shovvm is characterized bv (1) an input conversion that generates an angular displacement of the beam proportional to the input current, (2) a pneumatic amplifier stage that converts the resulting angii-...

Electronic (4- to 20-mA) signals are represented by dashed lines. In Fig. 8-49, these include the signal from the transmitter to the controller and the signal from the controller to the I/P transducer. Pneumatic signals are represented by solid lines with double crosshatching at regular intervals. The signal from the I/P transducer to the valve actuator is pneumatic. 

FIG. 8-87 Current-to-pressure transducer component parts. (a) Direct-cur-rent-pressure conversion. (b) Pneumatic booster amplifier (relay), (c) Block diagram of a modern I/P transducer. 

FIG. 8-73 Current to pressure transducer components parts (a) direct current to pressure conversion (b) pneumatic booster amplifier (relay) (c) block diagram of a modem I/P transducer. 

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