Modbus-RTU Digital I/O Modules 901MB 902MB 903MB

These modules provide 12 discrete input and/or output channels. They contain isolation which separates the I/O, power and network circuits. Network communication follows the industry standard RS-485 Modbus-RTU protocol.

The difference in the models are:

901MB contains 12 input channels, 902MB has 12 output channels and 903MB has 12 input or output channels.

The Acromag 901MB, 902MB and 903MB are Modbus-RTU Digital I/O Modules.

Firstly, open drain outputs are for current sinking or low side switching applications. The buffered inputs are active low. Which means they complement models 903, 905 and 906. As these units have open source, high side output switches and active high inputs. The socketed pull up resistors are removable or swappable depending on your application requirements.

The 903MB model has 12 input/output points and may be used as either on a bit by bit basis. Outputs read back to verify output settings. With a multichannel design in a rugged case makes this the perfect reliable module for control room and distributed field I/O applications.

Features of the Modbus-RTU Digital I/O Modules 901MB 902MB 903MB include:

  • Standard Modbus RTU protocol with high-speed RS-485 communication (up to 115K bps)
  • Twelve I/O channels in a single inch-wide unit reduces system costs and saves panel space
  • High-voltage, high-current, open-drain outputs enable direct (low-side) control of external devices
  • High-voltage buffered inputs monitor discrete levels from a variety of industrial devices
  • Tandem input/output circuitry (903 models only) connects input buffers with open-drain outputs for convenient loop-back monitoring of the output state
  • Outputs have built-in over-temperature and over-current shut-down protection, plus active clamping circuits for switching inductive loads
  • Watchdog timers provide a configurable fail-safe output state for use when host I/O communication is lost
  • Three-way isolation eliminates potential ground loops between power, I/O, and network circuitry
  • Self-diagnostics monitor micro controller activity to detect operational failures (lock-up) and execute a reset to restore communication
  • Operating temperature: -25°C to 70°C


Finally, for more information, contact us.


There are no reviews yet.

Only logged in customers who have purchased this product may leave a review.