11.5.3 Valve position feedback
In Fig. 11.18a a globe valve operated by an electric motor is shown. The screw
driven by the motor can move the plug in the valve up or down. A potentiometer
wiper is attached to the valve stem and gives a resistance directly proportional
to the amount the valve is open. This resistance value can be fed back to
the controlling electronics, so that the position of the valve can be monitored.
The system could also be digital, in which case, a digital encoding technique
would be used for feedback.