The most important registers
The registers for Modbus TCP and Modbus RTU are identical. All registers listed here are read-only and are queried with function code 03 (Read Holding Registers).
| Reading | Register | Data type | Unit |
|---|---|---|---|
| Active energy import L123 total | 6000 | uInt64 (4 registers) | Wh |
| Active energy import L123 tariff 1 | 6004 | uInt64 | Wh |
| Active energy export L123 total | 6020 | uInt64 | Wh |
| Active energy import L123 total | 8000 | uInt32 (2 registers) | kWh |
| Active energy export L123 total | 8010 | uInt32 | kWh |
| Active power L123 | 9000 | float | W |
| Current L123 | 9100 | float | A |
| Voltage L1-N | 9200 | float | V |
| Power factor L1 | 9300 | float | – |
| Frequency | 9310 | float | Hz |
| Serial number | 5000 | uInt32 | – |
The manual counts registers from 1. If your Modbus client starts at 0, subtract one: register 6000 becomes 5999. The meter delivers big endian; the word order is MSB before LSB.
Is the readout correct? The test registers
From register 4000 there are fixed test values. If something else comes back, it is almost always the byte or word order, data type or number of registers that is set incorrectly.
| Register | Data type | Expected value |
|---|---|---|
| 4000 | uInt32 | 4042260735 |
| 4006 | sInt32 | -42260735 |
| 4012 | uInt64 | 17361393123323912609 |
| 4036 | float | 1.234567 |
| 4040 | float | -1234567.89 |
Example with modpoll
Active power total as float and active energy import total as 64-bit value:
modpoll -1 -m tcp -t 4:f32 -i -f -r 9000 -c 1 <meter IP>
modpoll -1 -m tcp -t 4:i64 -u -i -f -r 6000 -c 1 <meter IP>Load profile via Modbus
From register 5900 you find the last completed load profile entry: timestamp, active and reactive energy in tariff 1 and 2, power, current, voltage, power factor and frequency. On meters with a serial number above 24000000, older entries can also be fetched: write the index with function code 16 to register 11098, wait until the same index is read back, then read from register 11100.
Larger quantities are easier to fetch via HTTP: http://<IP>/data/ returns up to 3000 load profile entries per request. More on the MID power meter with load profile page.
Setting up the network
- By default the meter obtains its IP address via DHCP. It is shown on the display under «Settings» → «IP address».
- In the web interface you can set a fixed IP address, the Modbus port and the TCP timeout (10 to 600 seconds, default 10).
- An NTP server keeps the clock synchronised. It must use a reference time valid for legal metrology.
- Access protection with a password secures the web interface (HTTP basic auth, user admin).
For security reasons, the tariff cannot be switched via Modbus TCP. This is only possible via the tariff inputs or on suitable Modbus RTU meters.
Directly or via the M-Center?
One Professional II TCP/IP per metering point is ideal when there is network everywhere and only a few meters are involved. With many meters or mixed media, the M-Center collects all values and provides them via a single IP address over Modbus TCP.
Order numbers
| Version | Article number | Shop |
|---|---|---|
| EMU Professional II 3/100 TCP/IP – direct connection 100 A | P20A000T | Shop: EMU Professional II 3/100 TCP/IP P20A000T → |
| EMU Professional II 3/5 TCP/IP – CT connection | P21A000T | Shop: EMU Professional II 3/5 TCP/IP P21A000T → |
Order online in the EMU Metering shop.