VARIABLE OUTPUT DEVICES
Variable output position indicators are summarized below.
Variable Position Indicator Summary
Potentiometer valve position indicators use an extension which is physically
attached to a variable resistor. As the extension moves up or down, the
resistance of the attached circuit changes, changing the amount of current flow
in the circuit.
An LVDT uses the extension shaft or control rod as a movable core of a
transformer. Moving the extension between the primary and secondary windings
of a transformer causes the inductance between the two windings to vary, thereby
varying the output voltage proportional to the position of the valve or control rod