AMR-OP75RHRC/01 control unit, temperature, humidity, CO2, touch graphic display, RS485, RTD/NTC, relay

Use cases

• Monitor indoor temperature, humidity, and CO2 levels on a live cloud dashboard for facility managers.
• Create an alert when CO2 concentration exceeds a threshold to trigger ventilation in classrooms or offices.
• Control the internal relay remotely to switch ventilation or signaling equipment from the cloud.
• Log RTD or NTC resistance values over time to detect sensor drift or calibration issues.
• Display outdoor temperature on the unit screen by writing the value from a remote weather source via the cloud.
• Track device status and firmware version across multiple installed units for maintenance planning.

Installation

1. 1Wire the AMIT AMR-OP75RHRC/01 RS485 A and B terminals to the corresponding RS485 port on your ModbusCloud gateway (MCG or MLP series), and connect the GND reference.
2. 2Configure the gateway serial port to 115200 baud, odd parity (1), and 8 data bits to match the device settings.
3. 3Set a unique Modbus RTU slave address on the AMR-OP75RHRC/01 and enter the same address in the ModbusCloud gateway configuration.
4. 4Import the AMIT AMR-OP75RHRC/01 template from the ModbusCloud template library and assign it to the correct gateway port and slave address.
5. 5Optionally configure a periodic write to register 100 every 30 seconds in the gateway to prevent the broken communication icon from appearing on the device display.
6. 6Verify that temperature, humidity, and CO2 readings appear correctly on the ModbusCloud dashboard before completing the installation.

Things to watch for

01

Why does the device display show a broken communication icon?

The AMR-OP75RHRC/01 expects a write to register 100 every 30 seconds. If this heartbeat write is not configured, the unit displays a warning icon. Data communication still works normally without it, but the icon may confuse end users.

02

What baud rate and parity settings are required?

The device requires 115200 baud with odd parity (1) and 8 data bits. Both the Modbus gateway and the device must use identical serial settings, otherwise communication will fail.

03

How do I write custom text to the touch display?

Each character position on the display has its own dedicated Modbus register. The template only includes key registers. Consult the AMIT device manual for the full register map and create additional registers in ModbusCloud as needed.

04

What register format is used for sensor values?

Temperature, humidity, CO2, and RTD values use Float32 (two consecutive 16-bit registers). Ensure the byte order (word swap) in your gateway matches the format specified in the AMIT documentation.

Registers (30)

16 read / 18 write

More AMIT templates

Amit DM-OT2 Modbus to OpenTherm

AMIT

Modbus RTU

Bridges Modbus RTU to OpenTherm for boiler monitoring and control.

19 registers15

More RTU templates

Alnor HRU-P

Alnor Systemy Wentylacji Sp. z o. o.

Modbus RTU

Controls Alnor HRU-P heat recovery ventilation units via Modbus RTU.

49 registers7

Alnor HRU

Alnor Systemy Wentylacji Sp. z o. o.

Modbus RTU

Controls and monitors Alnor heat recovery ventilation units via Modbus RTU.

29 registers13

Wattsonic - Schmachtl Sun Energy Box

Wattsonic

Modbus RTU

Monitors Schmachtl Wattsonic hybrid inverter via Modbus RTU

92 registers72

Heidelberg Wallbox Energy Control

AMPERFIED GmbH

Modbus RTU

Controls and monitors Heidelberg Wallbox Energy Control EV charger via Modbus RTU.

22 registers67

connecdoor.controller

connecdoor

Modbus RTU

Controls and monitors smart door access points via RS485

0 registers53

Belimo Air-Water Actuator Modbus RTU

Belimo

Modbus RTU

Controls communicative damper and valve actuators via Modbus RTU.

20 registers46