Circutor CEM-C31

Compatibility

Compatible with EpiSensor Edge over Modbus RTU

The CEM-C31-485-T1 and CEM-C31-485-DS, with or without MID, are compatible with EpiSensor Edge over their RS-485 Modbus RTU port, read through a ZMB-31 Modbus Interface or a Gateway serial port. Circutor's manual lists FC03 and FC04 reads and a hexadecimal map of energy, voltage, current and power registers with sizes and units, and its own frames confirm the address convention.

CEM-C31-485-T1 and CEM-C31-485-DS, MID or not (the CEM-C31-485-T1-MID is code Q23522), using instruction manual M017B01-03-23A. The CEM-C31-T1 has an optical port instead of RS-485 and is not covered. Site check: compare the first voltage read with the display; the same read shows the word order. Read-only monitoring: no FC10 writes and no FC05 partial-energy reset.

Connect it with

• Modbus Interface ZMB-3X From €399 ex VAT Configure
• Gateway ZGW-20 From €899 ex VAT Configure

Models

Specifications

A four-module DIN-rail energy meter for three-phase four-wire circuits measured through current transformers. It counts imported and exported active energy and reactive energy by quadrant, and shows per-phase voltage, current, power and power factor. The order code fixes the communication option, the input or output on terminals 21 and 22, and whether the meter records 2 quadrants, 4 quadrants or absolute energy.^1, 2

Versions

CEM-C31-T1, CEM-C31-485-T1 and CEM-C31-485-DS, each with a MID version. CEM-C31-485-T1-MID is code Q23522; Circutor names the CEM-D311-MID (Q23612) as its replacement.^1, 2

Current inputs

Through current transformers, 5(10) A: reference current 5 A, maximum 10 A, minimum 0.05 A, starting current 0.010 A. The primary and secondary ratios are set in the metrological setup menu.^1, 2

Voltage inputs

Three-phase four-wire, 3 × 57/100 V to 3 × 230/400 V depending on the version; 50 Hz, 60 Hz or automatic 50/60 Hz by order code. The manual also draws a single-phase connection.²

Accuracy

MID versions: active energy class B to EN 50470-3. Other versions: class 1 to IEC 62053-21. Reactive energy class 2 to IEC 62053-23.^1, 2

Auxiliary supply

Terminals 13 and 14, 230 V ~ or 230/400 V ~ depending on the version, ±20 %, 50 to 60 Hz, under 2 W. Check the label on the installed meter.^1, 2

RS-485

485 versions only: terminal 23 B(-) and 24 A(+). Modbus RTU, peripheral address 1 to 254 (default 1), 9600, 19200 or 38400 bit/s (default 9600), 8 data bits with no, even or odd parity and 1 or 2 stop bits (default 8N1). Up to 32 devices and 1200 m of shielded twisted pair.²

Inputs and outputs

485-T1: optocoupler pulse output on 21 (collector) and 22 (emitter), up to 24 V and 50 mA, programmable for kWh or kvarh. 485-DS: self-powered 5 V digital input on 21 and 22 for tariff selection or pulse counting.²

Display

LCD up to 999999.9 kWh, two buttons (the setup button can be sealed) and two test LEDs at 20000 imp/kWh and 20000 imp/kvarh.^1, 2

Environment

Operating -25 to +70 °C, storage -35 to +80 °C, 5 to 95 % relative humidity without condensation, up to 2000 m.²

Housing

Four DIN modules, polycarbonate, IP51 installed and IP40 at the terminals. Measurement terminals take 16 mm² (10 mm² with a ferrule); supply, I/O and RS-485 terminals take 1.5 mm².^1, 2

Interface

Documented measurements and integration boundaries for CEM-C31.

• All map addresses are hexadecimal and go on the wire as printed: 0x0732 is sent as 07 32 (decimal 1842). Read with FC03 or FC04; the map's writes use FC10 and the partial-energy reset uses FC05. Request exactly the number of registers the variable occupies.
• Phase 1, 2 and 3 voltage at 0x0732, 0x0734 and 0x0736: two registers each, volts with one decimal place, so divide by 10. Table 20 gives these as primary values, so the programmed transformer ratios are already applied.
• Phase 1, 2 and 3 current at 0x0738, 0x073A and 0x073C: two registers each, amps with two decimal places, so divide by 100.
• cos φ for phases 1, 2 and 3 at 0x073E, 0x0740 and 0x0742: two registers each with two decimal places. The map has no total power factor and no frequency register.
• Active power for phases 1, 2 and 3 at 0x0746, 0x0748 and 0x074A, and total active power at 0x074C: two registers each in W. Reactive power follows at 0x074E to 0x0754 in var and apparent power at 0x0756 to 0x075C in VA, total last in each group.
• Imported active energy at 0x0000 and exported active energy at 0x0002: two registers each in Wh. Reactive energy by quadrant at 0x0004 (Q1), 0x0006 (Q2), 0x0008 (Q3) and 0x000A (Q4) in varh. Exported energy, Q2 and Q3 are marked for the 4-quadrant version only.
• Partial counters repeat the same order from 0x0030 to 0x003A. They can be cleared from the setup menu and by FC05 to 0x0800, so use the totals from 0x0000 for consumption records.
• On the CEM-C31-485-DS with the input set to tariff, tariff 1 energy starts at 0x0100 and tariff 2 at 0x010C, total then partial, in the same order as the totals.
• Identity: the model description at 0xF010 is six registers of ASCII, coded as in Table 24 (one character gives 2 quadrants, 4 quadrants or ABS). Serial number at 0x0060, firmware version at 0x0050 to 0x0052, total operating time in seconds at 0x00C6.
• Configuration is readable and writable with FC10: transformer ratios at 0x044C to 0x0452, Modbus address at 0x03E8, speed at 0x03E9 and frame format at 0x03EA. Keep them out of a monitoring poll.

Setup

1. Identify the meter

   Read the model on the label and confirm a 485 version: CEM-C31-485-T1 or CEM-C31-485-DS, with or without MID. Note whether it records 2 quadrants, 4 quadrants or absolute energy, and confirm the CT ratio with the installer.

2. Read the serial settings from the setup menu

   A long press opens the general setup menu, which shows the peripheral address, speed and frame format (for example 8n1). Enter the same values in the Edge serial client or the ZMB-31 and leave the meter's own settings unchanged.

3. Wire the RS-485 pair

   Connect A(+) to terminal 24 and B(-) to terminal 23 with shielded twisted pair, keep the bus under 1200 m and 32 devices, and give each meter its own peripheral address.

4. Make one voltage read

   Send FC04 to address 0x0732 for two registers, as in the worked read below. One of the two words reads zero; that tells you the word order. Divide by 10 and compare with phase 1 voltage on the display.

5. Add the points you need

   Add current, power and the energy counters with the same word order. Use the total counters from 0x0000 rather than the resettable partial counters, and keep FC10 and FC05 out of the polling configuration.

Common questions

Is 0x0732 register 732 or 1842?

1842. Circutor states that all Modbus map addresses in the CEM-C31 manual are hexadecimal, and its example frames send them as printed. Enter 0x0732 in a client that takes zero-based addresses. A client with one-based labels calls the same register 1843, or 31843 for FC04.²

Which word of a 32-bit value comes first?

The manual does not say. Read a phase voltage first: in tenths of a volt it fits in one word, so the other word is zero and shows which half is the high word. Apply the same order to current, power and energy, and check one energy counter against the display.²

Why does exported energy read zero or return an error?

Exported active energy at 0x0002 and Q2 and Q3 reactive energy are marked for the 4-quadrant version only. A 2-quadrant meter records consumed energy only, and an ABS meter adds consumed and generated energy into one imported counter. The model description at 0xF010 and the label show which version is installed.²

Where are frequency and total power factor?

Table 20 lists voltage, current, cos φ and active, reactive and apparent power per phase, plus total power, but no frequency and no total power factor register. If you need a total power factor, calculate it in Edge from total active power at 0x074C and total apparent power at 0x075C.²

Which serial number address is right?

Table 23 lists the serial number at 0x0060 as 32 bits, while the read example in section 7.2.2.1 requests it at 0x2710. Use the table address, and do not rely on the serial number to identify a meter until one of them agrees with the label.²

Is the CEM-C31-485-T1-MID still sold?

Circutor's product page for Q23522 says to check availability and names the CEM-D311-MID (Q23612) as its replacement. That model has its own documentation; do not assume it uses this map.¹