Modbus RS-485 Current Input for PLC and Monitoring Systems
Connect current-output sensors and transmitters to PLC and monitoring systems with the ROI-IOM Series. Four analog current inputs accept signals from 0 to 25 mA, including standard 4-20mA measurement signals, with RS-485 connectivity for industrial monitoring and control applications.
Bring industrial current signals onto an RS-485 I/O platform
The Robert Owen Inc. ROI-IOM Series provides four analog current inputs for acquiring signals from current-output sensors, transmitters, and signal conditioners. Each input supports a 0 to 25 mA range, making the module suitable for common 0-20mA and 4-20mA measurement applications.
- Four current inputs — AI1 through AI4
- 0 to 25 mA range — supports standard industrial current signals
- RS-485 connectivity — integrate measurements with PLC and monitoring systems
For power, environmental, mechanical, communications, and all other I/O specifications, see the ROI-IOM Series technical specifications .
Current input capabilities
- 4 analog current inputs: AI1–AI4
- 0 to 25 mA input range
- 120 Ω input impedance
- 12-bit SAR ADC with 8.7 ENOB
- 500 kS/s maximum ADC sample rate with 48 MHz clock
- 15 m maximum specified cable length
Current input specifications
Four 0 to 25 mA analog inputs
AI1 through AI4 provide four independent analog current measurement channels. Each channel has an input range of 0 to 25 mA and a specified input impedance of 120 Ω.
Direct support for 4-20mA signals
The ROI-IOM 0 to 25 mA input range covers standard 4-20mA sensor transmitter and signal conditioner outputs. This allows common industrial process signals to be acquired without requiring separate factory-set current-range models.
On-board analog-to-digital conversion
The current inputs use a 12-bit SAR ADC specified at 8.7 effective number of bits (ENOB), with a maximum ADC sample rate of 500 kS/s when operated with a 48 MHz clock.
RS-485 connectivity for current measurement
The ROI-IOM communications interface provides RS-485 half-duplex operation with manual or automatic transmit/receive management. Supported baud rates range from 1200 to 115200, allowing acquired current measurements to become part of a connected industrial monitoring or control system.
Current measurement path
- Connect the signal — wire the current-output sensor or transmitter to one of AI1–AI4.
- Acquire the measurement — the ROI-IOM converts the analog current input into a digital measurement.
- Use the result — integrate the measurement into the connected PLC, controller, or monitoring application.
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Learn more →Need to connect a current-output sensor?
Tell Robert Owen what sensor or transmitter you need to measure and where its measurement needs to go. We can help with sensor signal conditioning, signal processing, I/O, and integration into the control or monitoring system.