The analog output system works similarly to the analog input system.  The analog output module reads the set of binary digits that indicate what the analog output status should be from the PLC output scan (usually determined by logic), and transforms those bits into the corresponding real world electrical signal level.

The analog output interface is usually connected to a controlling device through a transducer.  The transducer converts the v0ltage or current from the output module into the proper real world state for the device.  Just as with the analog input system, there is a large but finite list of output voltage and current ranges produced by most PLC manufacturers.

Common Analog Output Interfaces

  • 4 to 20 mA (current)
  • 10 to 50 mA (current)
  • 0 to 5 volts DC
  • 0 to +10volts DC
  • -5 volts to +5 volts DC
  • -10 volts to +10 volts DC