Regmet RK-CHM-D ... TFT touch screen controller

Use cases

• Monitor CO2 concentration, humidity, and temperature on a live cloud dashboard for each controlled zone.
• Adjust required temperature, humidity, and CO2 setpoints remotely without visiting the installation site.
• Create an alert when CO2 concentration exceeds a defined threshold for more than 5 minutes.
• Log indoor air quality data over time to generate reports for building management or compliance audits.
• Switch between operating modes remotely to adapt ventilation strategies to occupancy schedules.
• Calibrate temperature and humidity offsets from the cloud to correct sensor drift after commissioning.

Installation

1. 1Wire the Regmet RK-CHM-D RS485 terminals (A and B) to the corresponding RS485 port on your ModbusCloud gateway (MCG or MLP series).
2. 2Set the Modbus slave address on the RK-CHM-D using the device menu or DIP switches, and ensure it does not conflict with other devices on the bus.
3. 3Configure the gateway serial port to 19200 baud, 8 data bits, odd parity (1), and 1 stop bit to match the RK-CHM-D communication settings.
4. 4Import the Regmet RK-CHM-D template from the ModbusCloud template library and assign it to the correct gateway and slave address.
5. 5Verify the connection by checking that live temperature, humidity, and CO2 readings appear on the ModbusCloud dashboard.
6. 6If sensor readings show a consistent offset, use the calibration registers (address 76 for temperature, address 77 for humidity) to apply corrections.

Things to watch for

01

No data appears on the dashboard after connecting the RK-CHM-D. What should I check?

Verify that the baud rate is set to 19200 with odd parity on both the gateway and the controller. Also confirm that the RS485 A and B wires are not swapped and that the correct Modbus slave address is configured in the template.

02

Temperature or humidity readings seem slightly off compared to a reference instrument. How do I correct this?

Use the calibration offset registers provided in the template. Register 76 adjusts the temperature offset and register 77 adjusts the relative humidity offset. Write the correction value to bring readings in line with your reference.

03

Can I control all 68 operating modes through the template?

The template supports writing to the mode selection registers for modes 1 through 4. These four mode slots can each be assigned one of the 68 possible modes defined in the RK-CHM-D configuration.

04

Do I need a termination resistor on the RS485 bus?

If the RK-CHM-D is at the end of the RS485 bus, enable or install a 120 ohm termination resistor at that point. Proper termination reduces communication errors, especially on longer cable runs.

Registers (23)

3 read / 20 write

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