ABB M1M 20 Modbus

Power and energy meter

M1M 20 Modbus, order code 2TAZ662012R2000, measures single- or three-phase circuits through conventional 1 A or 5 A CTs. Its isolated serial interface connects to Edge for voltage, current, power and power-factor monitoring. Select this exact communications version before applying the M1M map.

ABB M1M 20 Modbus panel power meter
  • Modbus RTU

Power and energy meter

Ask an engineer

Compatibility

Compatible with EpiSensor Edge over Modbus RTU

ABB publishes the serial interface, FC03 reads and model-specific register widths and resolutions.

M1M 20 Modbus with conventional CT inputs. Start with the M1M20 applicability column in protocol 1.3 and user manual revision C. At commissioning, confirm the installed order code, firmware, marked accuracy class, CT ratio and wiring, then compare the first reading with the display.

Connect it with

For the M1M 20 Modbus serial version

  • Modbus
  • Edge
  • Platforms
Power and energy meter
Interface
Gateway
Edge
Output
M1M 20 ModbusM1M 20 Modbus serial port
Isolated serial interfaceApproved RS-485-to-host adapter
ZGW-20 GatewayHosts Edge locally
EpiSensor EdgeModbus client + register map
Customer platformMQTT · API · files
Modbus RTU · RS-485
Isolated serial
Runs locally
Optional onward data
Match the configured address, baud rate, parity and stop bits. Use a line bus with short stubs and end termination, following ABB’s wiring instructions. Keep one master on the segment. The customer-platform output is optional; Edge remains the local system of record.

Models

Download
ModelsInterfaceRoute into Edge
M1M 20 Modbus · 2TAZ662012R2000Isolated RS-485 and conventional 1 A/5 A CT inputs; no digital I/O on this version.Use its serial port for local measurement reads.
M1M 20 / Ethernet / I/O / I/O ProSeparate versions provide no communications, Ethernet or additional I/O.Identify the label and terminals; a similar front panel does not establish the installed interface.

Specifications

The conventional-CT serial model suits electrical panel monitoring. Its M1M protocol is a separate source from the M4M family map. Choose complete supported quantities and reject unavailable raw markers before scaling.12

Exact version
M1M 20 Modbus · 2TAZ662012R20003
Measurement inputs
1 A or 5 A CT secondary; 50 mA–6 A input range. Voltage range 80–265 VAC L-N.1
Accuracy in current manual
Revision C states active-energy class 0.5 to IEC 61557-12 and class 0.5S to IEC 62053-22; voltage/current class 0.5. CT and installation errors remain additional.1
Auxiliary supply
100–230 V AC/DC ±15%, maximum 5 VA.1
Serial settings
Address 1–247; 9600, 19200, 38400, 57600 or 115200 bit/s; odd/even parity with one stop bit, or no parity with one/two stop bits.1
Panel environment
96 × 96 × 85 mm; front IP51, terminals IP20; operating −5 to +55 °C; humidity up to 95% without condensation.1

Interface

Documented measurements and integration boundaries for M1M 20 Modbus.

  • L1 voltage at 0x5B02: two unsigned registers, 0.1 V resolution. L1 current at 0x5B10: two unsigned registers, 0.01 A resolution.
  • Total active power at 0x5B1A: two signed registers, 0.01 W resolution. Total power factor at 0x5B40: one signed register, 0.001 resolution.
  • Import/export active energy at 0x5000/0x5004 occupies four registers per value. Edge’s Modbus client does not read these 64-bit counters. Use the meter display for those totals; do not decode a partial counter.

Assessment

M1M 20 Modbus with conventional CT inputs and its documented serial interface.

InteroperabilityWell supported
A published Modbus RTU map gives FC03, addressing, types and model applicability for a standard serial connection.2
AccuracySupported with conditions
CT ratios, wiring mode and the documented accuracy conditions define the measurement. Complete 32-bit electrical readings are usable; four-register energy totals exceed Edge’s Modbus read width.12
SecurityLimited
The configuration menu has a password and ABB requires network safeguards. Plain serial Modbus does not authenticate or encrypt the read path; restrict physical and network access and keep monitoring read-only.12
ReliabilitySupported with conditions
The manual defines a ±15% auxiliary-supply tolerance and names IEC 61326-1 EMC and IEC 61010-1 safety requirements. Keep the supply and panel environment within the documented limits.1
RuggednessSupported with conditions
IP51 applies to the front and IP20 to the terminals. The −5 to +55 °C, non-condensing envelope calls for a suitable panel enclosure.1
ScalabilitySupported with conditions
Addresses 1–247, a line bus and defined serial rates support multi-meter polling. The address range is not a guarantee that 247 meters fit one physical segment.12
LifecycleSupported with conditions
ABB provides a current revision C user manual and a versioned M1M protocol. Keep the installed identity and source revision with the configuration when replacing meters.12

Setup

Read L1 phase voltage

Protocol 1.3 defines FC03, big-endian data and the M1M20 L1-voltage row on page 12.

Function
FC03 Read Holding Registers
PDU address and length
0x5B02 = 23298; 2 registers
Request PDU
03 5B 02 00 02
Synthetic response data
00 00 08 FC → unsigned 2300 × 0.1 V = 230.0 V
Acceptance
Compare with L1-N on the meter display in a wiring mode that provides phase voltage.

Acceptance: The 230.0 V value is a calculated example, not a device capture. The RTU client supplies the configured slave address and CRC. Retain only read operations in the monitoring poll.

  1. Confirm CT and wiring settings

    Have the authorised installer verify the wiring mode, CT primary/secondary ratio and any voltage transformer ratio. L1-N voltage is not available in every wiring system.

  2. Copy the actual communications settings

    Read CONF / COMM / ADDR, BAUD and BYTE from the meter. Match them in Edge. Do not change meter configuration or reset energy totals as part of this read check.

  3. Read one complete value

    Use FC03 with start address 0x5B02, decimal 23298, and quantity 2. The M1M example sends the hexadecimal table address directly; do not subtract one or add a 40001 reference prefix.

  4. Compare before extending the point list

    Decode an unsigned 32-bit value, high word first, then multiply by 0.1 V. Reject FFFF unavailable markers before scaling. Compare with the simultaneous L1-N display, then add current and signed power using their own widths and scales.

Common questions

Can I use an M4M template because the addresses look similar?
Use the M1M source and its product-applicability column. Similar addresses do not establish identical hardware, functions or firmware scope.2
Why is voltage unavailable?
ABB uses FFFF for data the configured device cannot measure or calculate. A three-phase three-wire system does not supply phase-to-neutral voltage. Treat unavailable as missing, not zero.2
Does this serial version provide Ethernet or I/O?
No. The user manual separates the Modbus, Ethernet, I/O and I/O Pro versions. Select the actual version before planning its connection or signals.1

Sources

  1. M1M 20 user manual, 2CSG445081D0201 revision C (opens in a new tab) ABB
  2. M1M Modbus manual, 9AKK108467A2704 version 1.3 (opens in a new tab) ABB
  3. M1M 20 Modbus official product record, 2TAZ662012R2000 (opens in a new tab) ABB

Further reading

Product names and trademarks belong to their owners. Publication does not imply endorsement or a commercial relationship.