An extra analog input that can be used in addition to the main process input.
This can provide functions such as remote setpoints, heater current measurement or valve position indication. Typical signal types are mA, mV, VDC or Potentiometer.
These signals are scaled to represent the desired input in the appropriate engineering units.
For example, a 4 to 20mA signal might be scaled so that 4mA equals 0.0%RH, and 20mA equals 100.0%RH.