4-20mA Sensor Transmitter Monitoring with RS-485
Connect 4-20mA sensor transmitters to PLC and monitoring systems with the ROI-IOM Series. Four analog current inputs accept industrial current signals from 0 to 25 mA, providing a compact DIN-rail interface for sensor monitoring and control applications.
Monitor industrial 4-20mA sensor transmitters
The 4-20mA current loop is widely used to carry sensor measurements in industrial monitoring and control systems. The ROI-IOM Series provides four analog current inputs for acquiring transmitter signals and making those measurements available to a connected control or monitoring system.
- Four current inputs — AI1 through AI4
- 0 to 25 mA input range — supports 4-20mA measurement signals
- RS-485 connectivity — integrate sensor measurements with industrial control and monitoring systems
For complete electrical, communications, environmental, mechanical, and 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
4-20mA current input monitoring
Acquire standard 4-20mA transmitter signals
Connect 4-20mA sensor transmitter outputs directly to the ROI-IOM analog current inputs. Each channel supports signals from 0 to 25 mA, covering the standard 4-20mA measurement range while also allowing measurement below and above the normal signal span.
Four independent analog current inputs
AI1 through AI4 provide four current measurement channels. Each input has a specified impedance of 120 Ω and uses the ROI-IOM on-board analog-to-digital conversion hardware.
RS-485-connected sensor monitoring
The ROI-IOM includes an RS-485 half-duplex communications interface with supported baud rates from 1200 to 115200, allowing acquired sensor measurements to become part of a connected PLC, controller, or monitoring application.
From 4-20mA transmitter to monitoring system
The ROI-IOM combines industrial current measurement with embedded processing and RS-485 communications. Multiple sensor transmitter signals can be brought into one DIN-rail I/O module and integrated with the equipment responsible for control, monitoring, trending, or data acquisition.
Three steps to monitor
- Connect the transmitter — wire its current signal to one of the AI1–AI4 analog current inputs.
- Acquire the measurement — the ROI-IOM converts the 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 monitor a 4-20mA sensor transmitter?
Tell Robert Owen what transmitters you need to monitor and where the measurements need to go. We can help with sensor signal conditioning, signal processing, I/O, and integration into your control or monitoring system.