Connectivity
What is isolated DIO? When do we need isolated DI/DO rather than standard DI/DO on a computer?
IPC247 engineering Answered on 2026-09-16
DIO (digital input/output) ports read push buttons, sensors and relay contacts, and output on/off signals to lamps, valves and relays. Isolated means the field-side circuit is electrically separated from the computer circuit, usually by optocouplers or magnetic isolation, withstanding a potential difference of about 1,500–3,000 VDC depending on the model.
Use isolated DIO when:
1. Signals are 24 VDC from a control cabinet with long wiring across the plant.
2. The machine is near drives, motors or welders, which are strong sources of noise and surges.
3. The sensor supply and the computer supply do not share a common ground.
Non-isolated DIO should be limited to short logic-level signals in the same cabinet on the same supply.
For wiring, check the datasheet for: dry-contact or wet-contact inputs, the voltage levels read as 0 and 1, NPN or PNP (sink or source) outputs, and maximum current per channel. Loads above that current must go through an interposing relay.