The RI-D175-MB is the M-Bus interface variant of Rayleigh Instruments‘ 45A direct-connect single phase energy meter. (Other variants offer only an S0 ‘pulse’ interface, or interface via Modbus rather than M-Bus.) It is a one-module wider meter with power terminals sized to accept cables up to 10.5mm².

Despite having an enclosure with the RI branding, this meter sends M-Bus telegrams which declare the Manufacturer to be PAD (i.e. PadMess GmbH) instead of RAY (or RIN) which are the allocated Rayleigh Instruments manufacturer codes. These meters are all shipped with their Primary M-Bus address set to 1 but they respond as expected to the various configuration tools which allow a new Primary address to be specified.

All instances of this meter model declare their ID (which is normally a serial number) to be 01000000 – and they do not use this as their Secondary M-Bus address. They do know about a ‘serial number’ – one is printed on a label attached to the side of the enclosure, and the same number is displayed on-screen (in two portions) at start-up and as the display cycles through all its parameters – but this appears to be ‘hidden’ from an M-Bus standpoint. Attempting to change the default ID using the Relay MBCONF utility doesn’t result in an error message, but it has no effect. As a result, it seems these meters are not compatible with meter management systems that rely on Secondary addressing.

Given that the website for PadMess GmbH says to refer to the website for Relay GmbH it seemed like it might be possible that MBCONF would recognise this meter, but that’s not the case – MBCONF only offers the option to apply ‘generic’ EN1434 configuration settings (e.g. to change the Primary address).

Using Primary addressing, these meters respond with the following M-Bus data points:

1. Total Energy
2. Voltage
3. Amperage
4. (Active) Power
5. Power Factor
6. Frequency
7. Tariff 1 Energy
   • Based on the supplied paper instruction leaflet but the online documentation for the Modbus registers says this is Import Energy
8. Tariff 2 Energy
   • Based on the supplied paper instruction leaflet but the online documentation for the Modbus registers says this is Export Energy

All the values in the M-Bus telegram are reported as Integers and some slightly curious units are used to (effectively) turn these into floating point numbers. For example, the Voltage is reported as e.g. 23720 in units of “1e-2  V” (i.e. hundredths of a Volt) – so that’s 237.20 Volts. This seems common practice for M-Bus systems and the M-Bus standard specifically caters for multiple sets of units that differ by factors of 10.

Using the wmbusmeters utility, an example M-Bus telegram received from one of these meters gets ‘analyzed’ as shown below. (This analysis deliberately used a driver which made no attempt to interpret the data field values, to avoid spurious interpretations of the readings.) Note that this was for a brand new meter that had not yet registered any energy consumption, which explains why many of the readings (correctly) show zero.

683C3C68080172000000012440010255000000_0C05000000000BFD478037020BFD590000000B2A0000000AFD3A00100AFD3A00500C05000000000C0500000000_EB16

000   : 68 start
001   : 3c length (60 bytes)
002   : 3c length again (60 bytes)
003   : 68 start
004   : 08 dll-c (RSP_UD2)
005   : 01 dll-a primary (1)
006   : 72 tpl-ci (long header)
007   : 00000001 tpl-id (01000000)
011   : 2440 tpl-mfct (PAD)
013   : 01 tpl-version
014   : 02 tpl-type (Electricity meter)
015   : 55 tpl-acc-field
016   : 00 tpl-sts-field (OK)
017   : 0000 tpl-cfg 0000 ( )
019   : 0C dif (8 digit BCD Instantaneous value)
020   : 05 vif (Energy 10² Wh)
021 C?: 00000000
025   : 0B dif (6 digit BCD Instantaneous value)
026   : FD vif (Second extension FD of VIF-codes)
027   : 47 vife (10^-2 Volts)
028 C?: 803702
031   : 0B dif (6 digit BCD Instantaneous value)
032   : FD vif (Second extension FD of VIF-codes)
033   : 59 vife (10^-3 Ampere)
034 C?: 000000
037   : 0B dif (6 digit BCD Instantaneous value)
038   : 2A vif (Power 10⁻¹ W)
039 C?: 000000
042   : 0A dif (4 digit BCD Instantaneous value)
043   : FD vif (Second extension FD of VIF-codes)
044   : 3A vife (Dimensionless / no VIF)
045 C?: 0010
047   : 0A dif (4 digit BCD Instantaneous value)
048   : FD vif (Second extension FD of VIF-codes)
049   : 3A vife (Dimensionless / no VIF)
050 C?: 0050
052   : 0C dif (8 digit BCD Instantaneous value)
053   : 05 vif (Energy 10² Wh)
054 C?: 00000000
058   : 0C dif (8 digit BCD Instantaneous value)
059   : 05 vif (Energy 10² Wh)
060 C?: 00000000
064   : EB crc
065   : 16 end

{
    "_":"telegram",
    "media":"electricity",
    "meter":"pad",
    "name":"",
    "id":"01000000",
    "timestamp":"2025-08-04T12:14:23Z"
}

Some commentary on the above:

• The first ‘dimensionless’ data point is the Power Factor, actually 1.000
• The second ‘dimensionless’ data point is the Frequency, actually 50.00

Rayleigh Instruments RI-D175-MB Meter by Marsh Flatts Farm Self Build Diary is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.