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reading Janitza UMG104 over Modbus RTU fails by float?


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Hi there,

i'm not able to read 32bit float big-endian from Janitza UMG104. Connection is over COM1 in Modbus mode, periodic trigger activated by pushbutton and set slave-name (bit) to 1.

This works fine for the Modbus TCP slave, which provide me system information. The powermeter i try to read, deliver me important informations which i later need to add together with sensor values to a data table.

Reading fails at the point, the 32bit float comes in.

I tried:

Register addresses 19018 (current, A), 19026 (power, W) and 19034 (power, VA) with own Tags as REAL, with memory float array MF[MF_0] to MF[MF_2], reading the registers from normal table (1639) and with adding address value for little endian communication. Nothing works.

Registers 19xxx provide most used values.

The REAL goes to a REAL to INT converter, ouput is INT32.

A try with GridVis and Janitza Modbus Diagnostic tool works fine, all 3 Register addresses with reading 4 bytes.

When i take a look the the online state of the memory floats, i see flickering data.

I will try the swap bytes extended, but i hope, you have generally an idea, what goes wrong and how i can fix this.

Pictures follows later, when i'm back to work :)

Enviroment: Janitza UMG104 (latest firmware), Unistream USP-156-B10 (latest firmware), Com1 38400/8/n/1 Modbus periodic, Modbus Slave ID 1.

(yes, I'm new to PLC/HMI)


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