Condition Monitoring

[Mahesh]

We're using Anybus gateway (DNet to Modbus) to integrate the XM data with Yokogawa PLC over modbus network. We'd mapped the data in the Anybus GTW and communication is also estabilished with the PLC. But the data displayed in the PLC is in binay format. The PLC guy want the High Count and Low Count for scaling purpose. Does anybody know what these value are ?

I'd attached the picture of the screen displaying the binary values for the selected modbus registers.

[pc · Accepted solution]

My guess is thta the PLC guys is not aware of how the XM module provides the data. Most systems provide a scaled value, which means you need the scaler, or high and low, to resolve the value. For XM we provide 32 bit the floating point value, so no need to scale anything.

Make sure that the bits are swapped (Big Endian vs. Little Endian) though as Modbus and XM (DeviceNet) do not use the same format, and the Anybus does not make the conversion for you.

[Mahesh]

Swapping of Byte and Words solved the issue.

[pc]

Scaled means data that is an integer number that represents a value between some minimum and maximum. It also means that your resolution is limited to the size of integer used.

XM data is not scaled. It is in 32 bit floating point format. So no scaler.

But with Modbus floating point values are maintained differently on different systems. On PC's and DeviceNet the binary format of the floating point value is different than on some SCADA systems (don't know if yours is or not). This format is called Little Endian / Big Endian.

Some Modbus devices do this conversion automatically. The Anybus device does not. So this conversion, if necessary, must be done in your PLC. More than likely your PLC guy will know what this all means and won't have a problem - if conversion is necessary since the problem may just be that he thought he was working with an integer.