Modbus RS-485 Sensor Monitoring for 4-20mA and 0-30 VDC Inputs
Connect current-output and voltage-output sensors to PLC and monitoring systems with the ROI-IOM Series. Four analog current inputs support signals from 0 to 25 mA, including standard 4-20mA transmitters, while four analog voltage inputs accept signals from 0 to 30 VDC. RS-485 connectivity provides a compact DIN-rail interface for industrial sensor monitoring and control applications.
Monitor current and voltage sensor signals on one I/O platform
Industrial sensors, transmitters, and signal conditioners commonly provide either current or voltage outputs. The ROI-IOM Series combines four analog current inputs and four analog voltage inputs in one DIN-rail I/O platform, allowing multiple types of sensor signals to be acquired by the same system.
- Four current inputs — AI1 through AI4 accept signals from 0 to 25 mA, including standard 4-20mA signals
- Four voltage inputs — AV1 through AV4 accept signals from 0 to 30 VDC
- RS-485 connectivity — integrate sensor measurements with PLC, controller, and monitoring systems
For complete electrical, communications, environmental, mechanical, and I/O specifications, see the ROI-IOM Series technical specifications .
Analog sensor input capabilities
- 4 analog current inputs: AI1–AI4
- 0 to 25 mA current input range
- 120 Ω current input impedance
- 4 analog voltage inputs: AV1–AV4
- 0 to 30 VDC voltage input range
- >450 kΩ voltage 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 analog input cable length
Sensor input options
Monitor 4-20mA sensor transmitters
AI1 through AI4 provide four independent analog current measurement channels. Each input supports signals from 0 to 25 mA with a specified input impedance of 120 Ω, covering standard 4-20mA sensor transmitter and signal conditioner outputs.
Monitor 0 to 30 VDC sensor signals
AV1 through AV4 provide four independent analog voltage measurement channels. Each input accepts signals from 0 to 30 VDC with an input impedance greater than 450 kΩ, allowing voltage-output sensors and signal conditioners to be connected to the ROI-IOM.
Combine current and voltage sensors in one system
The ROI-IOM provides both current and voltage measurement channels in the same I/O platform. Applications that include a mixture of 4-20mA transmitters and DC voltage-output sensors can acquire both signal types without using separate current-only and voltage-only I/O modules.
Industrial sensor monitoring with flexible analog inputs
4-20mA transmitters
Acquire standard 4-20mA measurement signals from industrial transmitters used for process and equipment monitoring. The ROI-IOM 0 to 25 mA input range covers the complete 4-20mA signal span.
Voltage-output sensors
Connect voltage-output sensors and signal conditioners to the ROI-IOM 0 to 30 VDC analog voltage inputs. The wide voltage input range supports common conditioned DC measurement signals.
Mixed sensor systems
Monitor current and voltage sensor signals with the same DIN-rail I/O platform. This provides a common interface for applications containing different sensor output types.
RS-485 sensor monitoring for PLC and control systems
The ROI-IOM combines analog sensor acquisition with an RS-485 half-duplex communications interface. Supported baud rates range from 1200 to 115200, allowing acquired current and voltage measurements to become part of a connected industrial monitoring or control system.
Instead of treating current-output and voltage-output sensors as separate monitoring applications, the ROI-IOM provides a common I/O platform for acquiring both signal types and making their measurements available to the connected system.
Sensor measurement path
- Connect the sensor — wire a current-output sensor to AI1–AI4 or a voltage-output sensor to AV1–AV4.
- Acquire the signal — the ROI-IOM converts the analog current or voltage input into a digital measurement.
- Use the measurement — integrate the acquired sensor value into the connected PLC, controller, or monitoring application through the RS-485-connected I/O system.
One platform for multiple sensor signal types
Process monitoring
Acquire analog measurements from transmitters and conditioned sensors used to monitor industrial processes, machinery, and equipment.
PLC sensor integration
Bring current and voltage measurements into PLC and controller applications through a compact RS-485-connected I/O platform.
Data acquisition
Collect multiple analog sensor signals for monitoring, trending, supervisory control, and industrial data-acquisition applications.
Related solutions
ROI-IOM Series
View complete analog I/O, communications, digital I/O, relay, power, environmental, and mechanical specifications.
View complete specifications →4-20mA sensor transmitter monitoring
Monitor standard 4-20mA sensor transmitter signals using ROI-IOM analog current inputs and RS-485 connectivity.
Learn more →Analog sensor signal conditioning
Convert sensor outputs into standard industrial current or voltage signals for measurement, monitoring, control, and data acquisition.
Learn more →Need to connect current and voltage-output sensors?
Tell Robert Owen what sensors or transmitters you need to monitor and where their measurements need to go. We can help with 4-20mA and voltage signal acquisition, sensor signal conditioning, I/O, and integration into your control or monitoring system.