Glossary · Electrical engineering and control panels
Analog output
Also known as: AO (I/O), Analog output channel
German: Analogausgang
In industrial control, an analog output is a controller output channel that converts a digital value from the control program into a continuous signal, such as 4–20 mA or 0–10 V, to drive actuators like control valves or frequency converters.
- Control panels
In one sentence
An analog output converts a digital value into a continuous signal such as 4–20 mA or 0–10 V to drive valves or drives.
Example
The PLC writes the PID output to an analog output, which sends 4–20 mA to the positioner of the steam valve.
How it applies
- Engineering: Define signal type, scaling and the substitute value the output takes when the controller stops or communication fails. That value must bring the actuator into a state that is safe for the process, a Safe default.
- Commissioning: Check the full range end to end: 0 percent and 100 percent in the program must correspond to closed and open at the valve, in the right direction.
- Documentation: Document scaling, units, direction (direct or reverse acting) and substitute value behavior for each channel. Service manuals should describe how to force an output for testing and the precautions required.
Analog output vs. relay or transistor output
An analog output provides a continuous signal. Relay output and Transistor output channels switch on and off. Proportional actuators need analog outputs or a fieldbus interface.