I/O modules form the critical interface between industrial control systems and the physical world. Understanding the differences between analog input modules, digital input modules, analog output modules, and digital output modules is essential for maintaining automation systems.
What Are Industrial I/O Modules?
Input/Output modules connect PLCs and DCS systems to field devices like sensors, transmitters, valves, and motors.
Analog Input Modules
Analog input modules convert continuous electrical signals into digital values.
Common Signal Types
- 4-20mA current loops – Industry standard for process transmitters
- 0-10V voltage signals – Common for position feedback
- Thermocouple inputs – Direct temperature measurement
- RTD inputs – Precision temperature measurement (PT100)
Popular Analog Input Modules
- ABB AI810 – 8-channel analog input for S800 I/O
- Allen-Bradley 1756-IF16 – 16-channel ControlLogix input
Digital Input Modules
Digital input modules monitor discrete (on/off) signals from field devices.
Applications
- Limit switches and proximity sensors
- Push buttons and selector switches
- Motor running status
- Valve position feedback
Popular Digital Input Modules
- ABB DI810 – 16-channel digital input for S800
- Allen-Bradley 1756-IB16 – 16-point DC input
Analog Output Modules
Analog output modules convert digital control signals into continuous electrical outputs.
Applications
- Control valve positioning
- Variable frequency drive speed reference
- Setpoint signals to controllers
Popular Analog Output Modules
- ABB AO810 – 8-channel analog output
- Allen-Bradley 1756-OF8 – 8-channel ControlLogix output
Digital Output Modules
Digital output modules switch discrete loads on and off.
Output Types
- Transistor outputs – Fast switching, DC loads
- Relay outputs – AC/DC capable, isolated contacts
Popular Digital Output Modules
- ABB DO810 – 16-channel digital output
- Allen-Bradley 1756-OB16 – 16-point DC output
Browse our selection of I/O modules from leading manufacturers.