Hi All,

We have inherited and site which has RI-D480 energy meters and a Desigo BMS system, these meters have never been integrated into the BMS,
Following manufacture instructions we have connected our RS-485 cable to Pin 1-6 of the RJ12 connector and installed a 120 Ohm resistor at the other side of the meters. We have tried multiple Modbus scanners and also through the TXI2, however we cannot seem to pick up any of the modbus registers or devices. Has anyone come across this before and has a solution or work around that may help.

 

I'm not familiar specifically with that energy meter, but I can provide general Modbus advice.

Typically, complete lack of communication (i.e. the master's requests are timing out), is caused by either a wiring issue or a communication setting issue. Although, there are more rare causes, such as device damage or the device doesn't actually support Modbus.

From the Rayleigh Instruction Manual (https://www.rayleigh.com/media/uploads/RI-D480-IM-V01.pdf), it appears that there are two different versions of the RI-D480 energy meter. One that supports Modbus (RI-D480-G-C) and one that supports M-Bus (RI-D480-G-MB). Note that although those two protocols sound similar, they are very different and very much not compatible with one another. Which meter do you have on site?

Assuming you have the RI-D480-G-C, then you may have a wiring or communication setting issue.

Wiring

• In addition to the + and - signals, RS-485 also requires a common-mode reference. In other words, all RS-485 device's must share a common 0V reference for their RS-485 signals. Non-isolated devices that have only + and - terminals typically use an earth ground connection as the RS-485 common-mode reference. Since your Rayleigh meter has only + and - connections on its RJ-12 connector, I would guess that it is non-isolated and its "N" (voltage supply neutral) terminal is what the RS-485 signals are referenced to. Therefore, any RS-485 device that you are connecting to the meter should also use an earth ground connection as its RS-485 common-mode reference.
• The 120 ohm termination resistor(s) should be removed for testing purposes. Termination, if used, should be applied at each end of the bus. Termination resistors are only required for long cable runs (several hundred or a thousand or more feet, depending on the baud rate used). Termination is used to absorb signal reflections that can interfere with the actual signal and cause communication errors. However, termination should not be used without considering and installing idle biasing on the bus (pulling the + signal up to 5V through a resistor and the - signal down to 0V through a resistor), as the RS-485 specification requires there be at least 200mV difference between the + and - signals for RS-485 receivers to function properly.

Communication Settings

• All communication settings must match between the master and slave(s), including baud rate, parity, and number of stop bits. It appears the default settings for the RI-D480-G-C is 9600 Baud, No Parity, 1 Stop Bit
• The master must target the correct slave address (a.k.a. slave ID) of the Modbus slave.
• Many devices require a power cycle for communication setting changes to take affect. Therefore, even though you may believe the settings match, if the meter has not yet been power cycled, it may not actually be using the settings shown in its configuration menu.

If you're not sure what the slave device's address (slave ID) is, you can try using Chipkin's CAS Modbus Scanner to scan for devices.
https://store.chipkin.com/products/tools/cas-modbus-scanner

Otherwise, here are my typical recommendations for Modbus master software:
ModScan
https://www.win-tech.com/

Simply Modbus
https://simplymodbus.ca/RTUmaster.htm

Modbus Poll
https://www.modbustools.com/modbus_poll.html