Connecting to Rayleigh Meter Using Modbus

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Thread Starter

Sarah Brown

Has anyone managed to connect to a Rayleigh meter RI-f-100C via Modbus register?

The Modbus register for KWh does not match what the meter reads.
 
Nope, never even heard of one until today.

Their web site does not appear to offer download of a manual, so generic Modbus advice applies:

1. You might be reading the wrong register, an input register rather than a holding register, or an adjacent register because of the one-offset due to zero or one based register addressing.

2. You might be reading only part of a value, half of a 32 bit long integer, or half of a 32 bit floating point value

3. You might be reading a 32 bit floating point value but interpreting the word/byte format incorrectly. There are typically two common 32 bit Floating point formats and most Modbus master/clients allow you to pick one of the two.

4. You might be reading the correct register, but the interpretation is incorrect because the value needs some arithmetic/math done on it to get the correct value.

For instance, integer values might need to be divided by a constant or multiplied by a factor to get the correct value. That type of information should be published in the device's register map or noted in the Modbus section of the manual.
 
Sarah
I have encountered this with the Rayleigh RI300 meters.
They read, but not the same values as the meter reads.
The Frequency reads correctly, as this is a Single Hex Work.
Where thare are two 'words' it appears that the Rayleigh reads the in reverse, making the figure wrong.
Spoke to Rayleigh. Not resolved.

The ModBus setup I am using works correctly on Scneider and Socomet Meters !!

Have you had any success.

I am speaking with Contemporary Controls, who may have a solution.
Regards
Joe Dixon
 
Hi,

Referring to page 3 (under readable parameter table) of the attached document shows data in Input Registers with data type float (2 registers). Floating points can be read as "little endian", "little endian byte swapped", "big endian" and "big endian byte swapped" so use any of these format to read KWH or other parameters (register staring from 30000). Sometimes you have to give offset of +1 to read float points like if you want to read 30000 then read 30001 as floating.

Regards,
Prasoon Tewari
 

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Has anyone managed to connect to a Rayleigh meter RI-f-100C via Modbus register?

The Modbus register for KWh does not match what the meter reads.
As I reported recently, I have also had this problem.
With the assistance of Robert Owen of Contemporary Controls, we have fitted and interface that 'reads' the ModBus Values Correctly, and also provides them as BACnet Points into the BMS.

Joe Dixon
 
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