Connecting to Rayleigh Meter Using Modbus


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.