Circutor CEM-C21

Installation

1. 1Wire the Circutor CEM-C21 to the ModbusCloud gateway (MCG or MLP series) using a shielded RS-485 cable, connecting A, B, and GND terminals.
2. 2Set a unique Modbus RTU slave address on the CEM-C21 using the front panel buttons, and note this address for gateway configuration.
3. 3Confirm the CEM-C21 baud rate is set to 9600 (factory default) to match the template settings.
4. 4In the ModbusCloud platform, add a new device and import the Circutor CEM-C21 template from the template library.
5. 5Enter the configured Modbus slave address in the device settings and verify that live readings appear on the dashboard.

Things to watch for

01

Why does the Cos phi F3 reading show incorrect values?

The Cos phi F3 register at address 1858 uses uint16 data format, while all other registers use int32. Ensure the register data type is set correctly. The ModbusCloud template already accounts for this difference.

02

The gateway cannot communicate with the CEM-C21. What should I check?

Verify that the RS-485 wiring is correct (A to A, B to B, GND to GND). Confirm the baud rate is 9600 and the slave address on the meter matches the address configured in the gateway. Check that the RS-485 bus is terminated if the cable run exceeds 10 meters.

03

Can I connect multiple CEM-C21 meters on the same RS-485 bus?

Yes. Assign each meter a unique Modbus slave address. Add a separate device entry in ModbusCloud for each meter using the same template. Ensure proper bus termination at both ends of the RS-485 line.

04

Does this template support reactive energy readings?

The template reads reactive power registers. Reactive energy measurement requires the optional class 2 variant of the CEM-C21. If your meter does not have this option, reactive registers may return zero.

Registers (11)

11 read / 0 write

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