What is the difference between SDM630 and SDM630MCT?

The direct-connected SDM630 carries the measured current through its terminals. SDM630MCT measures the secondary of external current transformers. CT secondary, ratio and phase wiring are therefore part of MCT commissioning; sharing a Modbus format does not make the hardware interchangeable.

For a 100/5 A CT, should I enter 100 or 20?

The V2 manual calls for CT2 = 5 A and CT ratio = 20, because 100 / 5 = 20. Do not confuse a ratio field with a primary-current field on another meter or generation. Once the meter scales measurements, applying 20 again in Edge would double-scale them.

Why does a valid response decode as a tiny number?

Check float32 decoding and register order. Protocol V1.7 defaults to the most significant register first but supports reversed order. Preserve the order configured on the installed meter and compare voltage with its display; changing meter settings is not necessary just to select the right client decoder.

Can the MID ratio be changed later?

The cited V2 manual warns that the MID-approved version provides only one opportunity to set the ratio. Treat approval and ratio setup as a commissioning decision for the exact variant. Do not use a register write to experiment with CT settings.

Can I reuse these specifications on a newer SDM630MCT?

Use the manual matching the installed generation. This page covers the V2 series and protocol V1.7. Later SDM630MCT and dual-tariff documentation can have different accuracy, configuration and electrical ratings. The model label, approval and firmware are the starting point.

Eastron SDM630MCT V2: CT ratio and Modbus setup

Compatibility

Compatible through Modbus RTU

Eastron publishes the serial protocol, measurement addresses and float format needed to configure an Edge Modbus client.

SDM630MCT V2 with the RS-485 Modbus RTU interface, covered by Eastron Europe’s V2 series manual and Modbus protocol V1.7. The M-Bus, direct-connected SDM630, Rogowski, TCP and newer-generation models need their own matching documentation. The downloadable starter is narrower: 1 A / 5 A CT input, 3P4W only, with normal word order. Confirm the installed CT settings and compare the returned word order with the meter display before applying it.

Connect it with

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

For the Modbus version of SDM630MCT V2

Modbus
Edge
Platforms

Use the meter’s configured address, baud rate, parity and stop bits. The meter’s external CT inputs are measurement connections; they are not the RS-485 bus. Read monitoring values with FC04 and leave settings unchanged during routine collection. The customer-platform output is optional; Edge remains the local system of record.

Specifications

Choose the MCT version when load current must be measured through external current transformers rather than passing through a direct-connected meter. A 100/5 A CT requires a 5 A secondary setting and ratio 20. The meter then reports primary-side measurements; applying that same ratio again in Edge would multiply readings twice. Wiring topology, phase association and CT polarity must also agree before power and energy are meaningful.¹

Current measurement: External CTs with 1 A or 5 A secondaries; configure secondary and primary-to-secondary ratio¹
Wiring systems: Single-phase two-wire, three-phase three-wire or three-phase four-wire¹
Active energy accuracy: Class 1 to IEC 62053-21 in the V2 manual; external CT error is additional¹
Auxiliary supply: 85–275 V AC or 120–380 V DC in the cited V2 manual; confirm the installed supply variant¹
Serial settings: 2400, 4800, 9600, 19200 or 38400 bit/s; none, odd or even parity; one or two stop bits¹
Meter address: 1–247, unique on the RS-485 segment¹
Other outputs: Two pulse outputs; pulse settings and RS-485 registers are different collection paths¹

Interface

This register map is for the SDM630MCT V2. SDM630MCT V2 Modbus, SDM630MCT V2 dual-tariff / MID versions and SDM630 direct-connected / MCT M-Bus / MCT-RC / MCT-TCP have their own interfaces and are not covered here.

Communication settings

Interface: RS-485 Modbus RTU; read the installed baud rate, parity and stop-bit settings
Unit address: 1–247; use the installed unique address, not broadcast address 0
Wiring scope: 3P4W only for this starter map
Read with: FC04 (input registers)
Word order: High word first on every value
Addresses: Zero-based PDU addresses, as sent on the bus

From SDM630MCT Modbus protocol V1.7² and SDM630 MCT V2 series installation and operating manual¹.

Register map

Download

Point	Address	Hex	Format	Scale	Unit
Voltage L1-N	0	`0x0000`	FLOAT32	×1	V
Voltage L2-N	2	`0x0002`	FLOAT32	×1	V
Voltage L3-N	4	`0x0004`	FLOAT32	×1	V
Current L1	6	`0x0006`	FLOAT32	×1	A
Current L2	8	`0x0008`	FLOAT32	×1	A
Current L3	10	`0x000A`	FLOAT32	×1	A
Active Power L1	12	`0x000C`	FLOAT32	×1	W
Active Power L2	14	`0x000E`	FLOAT32	×1	W
Active Power L3	16	`0x0010`	FLOAT32	×1	W
Total Active Power	52	`0x0034`	FLOAT32	×1	W
Total Apparent Power	56	`0x0038`	FLOAT32	×1	VA
Total Reactive Power	60	`0x003C`	FLOAT32	×1	VAr
Total Power Factor	62	`0x003E`	FLOAT32	×1	-
Frequency	70	`0x0046`	FLOAT32	×1	Hz
Import Active Energy	72	`0x0048`	FLOAT32	×1	kWh
Export Active Energy	74	`0x004A`	FLOAT32	×1	kWh
Import Reactive Energy	76	`0x004C`	FLOAT32	×1	kVArh
Export Reactive Energy	78	`0x004E`	FLOAT32	×1	kVArh
Neutral Current	224	`0x00E0`	FLOAT32	×1	A

Download the SDM630MCT V2 register map as CSV

Assessment

SDM630MCT V2 with the RS-485 Modbus RTU interface, covered by Eastron Europe’s V2 series manual and Modbus protocol V1.7. The M-Bus, direct-connected SDM630, Rogowski, TCP and newer-generation models need their own matching documentation.

InteroperabilityWell supported: A manufacturer protocol defines local FC04 measurements, float32 lengths and configurable register order.²
AccuracySupported with conditions: The V2 manual specifies measurement accuracy and CT scaling. Transformer error, wiring and one-time MID settings affect suitability.¹
SecurityNot yet assessed: Configuration is password-protected, but the cited documents do not establish authenticated or encrypted telemetry.^1, 2
ReliabilitySupported with conditions: Documented measurement and serial settings support fault diagnosis; valid communication alone does not prove phase or ratio correctness.^1, 2
RuggednessNot yet assessed: Installation and supply requirements are documented; application-specific environmental qualification needs the exact order variant.¹
ScalabilitySupported with conditions: Configurable addresses and serial rates permit shared-bus polling, with complete register pairs and one address per meter.²
LifecycleNot yet assessed: Public V2 documentation remains available, but that does not establish an end-of-sale or long-term support commitment.¹

Edge template

This JSON file supplies the register map. Applying it to an existing meter replaces its sensor list while retaining the site connection, unit ID and enable state.

Model	Connection	Points	Version	Updated	Download
SDM630MCT V2	Modbus	19	1.0.0	1 Oct 2026	Download

Downloads need a signed-in account with Edge download access.

Use the template in Edge

Import the JSON file
In Edge, open Settings, then Devices and Templates. Choose Import JSON and select the downloaded file. Confirm that the model and template name match your device.
Load the map for your meter
For a new Modbus device, use Load Template before entering the manufacturer or model; it fills those fields and the register list. Set the name, site connection and unit ID, check the polling enable state, then test before saving. For an existing device, apply only to the matching model; this replaces its sensor list but retains its connection, unit ID and enable state.
Test a reading
Use Test in the wizard and compare a known reading with the meter display. Check its unit, sign and scale, then confirm that timestamps keep advancing. These starter maps are read-only and leave exports off until you configure them.

Setup

Read a complete phase voltage

Protocol V1.7 places phase 1 line-to-neutral voltage at input reference 30001, PDU address 0, as a four-byte float in V.

Function: FC04 Read Input Registers
Request PDU: 04 00 00 00 02: address 0, quantity 2 registers
Address 1 RTU frame: 01 04 00 00 00 02 71 CB, including CRC low byte first
Independent decoder example: 43 66 00 00 decodes to 230.0 V with high register first. A reversed register configuration returns the two words in the opposite order.
Scaling: Float32 in V; no CT multiplier belongs on this voltage reading.

Acceptance: The bytes are a synthetic decoder example, not a device capture. Accept the actual read only when the returned word order and value agree with the meter display. The protocol permits reversed register order, so a default assumption is insufficient.

Identify the CT-input Modbus version
Record SDM630MCT V2, its communication suffix, firmware and approval markings. Confirm that the installed current transformers have a compatible 1 A or 5 A secondary. A direct-connected SDM630 and a Rogowski-input model are different measurement arrangements.
Set topology and CT scaling once
For a 100/5 A CT, choose CT2 = 5 A and CT ratio = 20, not 100. The V2 manual states that the MID-approved version allows the ratio setting only once. Have the installation and ratio checked before committing that setting; do not change it as a communications diagnostic.
Match the serial settings
Read the meter’s address, speed, parity and stop bits and set the Edge client to match. Give every meter a unique address. Start with one meter and one measurement, keeping communication errors separate from a genuine zero reading.
Verify voltage before interpreting CT readings
Read two input registers at PDU address 0 with FC04. Decode float32 using the meter’s configured register order and compare with the simultaneous display. Voltage is a useful first check because it does not depend on the CT ratio.
Check current, direction and energy
Compare each phase current and total active power with the display under a known load. Verify CT phase association and import/export direction. Do not multiply the returned measurements by the CT ratio again. Check a changing import or export energy counter over a measured interval before using it for totals.

Before you rely on the decode

This starter is for the SDM630MCT V2 RS-485 model with 1 A / 5 A CT inputs, configured for three-phase four-wire (3P4W) measurement. Other wiring systems can return zero for unsupported points; do not interpret those zeros as measurements.

The meter can reverse its register order. This file assumes the documented normal order: big-endian bytes, high register first, no word or byte swap. Compare a non-zero voltage with the front panel before accepting the map; change the client decoder to match the installed meter if necessary.

Commission CT secondary current and CT ratio on the meter first. For a 100/5 A CT, the manual specifies CT2 = 5 and ratio = 20. The map uses the published engineering units with multiplier 1; confirm current and power against the panel and do not apply a second CT ratio.

Protocol document V1.7 is not a firmware version. No numeric firmware minimum is specified in these sources. Confirm the exact V2 model and matching documentation before use. This researched template has not been physically validated on a meter.

Read complete two-register values. Keep transactions within 60 registers, the stricter limit in the protocol. The selected sparse points form separate contiguous blocks; do not merge gaps or add points without reviewing the resulting request sizes.

Common questions

What is the difference between SDM630 and SDM630MCT?: The direct-connected SDM630 carries the measured current through its terminals. SDM630MCT measures the secondary of external current transformers. CT secondary, ratio and phase wiring are therefore part of MCT commissioning; sharing a Modbus format does not make the hardware interchangeable.¹
For a 100/5 A CT, should I enter 100 or 20?: The V2 manual calls for CT2 = 5 A and CT ratio = 20, because 100 / 5 = 20. Do not confuse a ratio field with a primary-current field on another meter or generation. Once the meter scales measurements, applying 20 again in Edge would double-scale them.^1, 2
Why does a valid response decode as a tiny number?: Check float32 decoding and register order. Protocol V1.7 defaults to the most significant register first but supports reversed order. Preserve the order configured on the installed meter and compare voltage with its display; changing meter settings is not necessary just to select the right client decoder.²
Can the MID ratio be changed later?: The cited V2 manual warns that the MID-approved version provides only one opportunity to set the ratio. Treat approval and ratio setup as a commissioning decision for the exact variant. Do not use a register write to experiment with CT settings.¹
Can I reuse these specifications on a newer SDM630MCT?: Use the manual matching the installed generation. This page covers the V2 series and protocol V1.7. Later SDM630MCT and dual-tariff documentation can have different accuracy, configuration and electrical ratings. The model label, approval and firmware are the starting point.^1, 2

Related devices

Sources

SDM630 MCT V2 series installation and operating manual (opens in a new tab) (PDF) Eastron Europe
SDM630MCT Modbus protocol V1.7 (opens in a new tab) (PDF) Eastron Europe

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