PM8000 Modbus Register and Wonderware

[dice1010]

I know this is a very specific question, but I'm hoping someone can help resolve this issue. We are hoping to start pulling in information from our PM8000 to our SCADA system using wonderware. I am using the default modbus registers. I have good quality in the connection to the device but only certain tags are pulling the correct information. For instance, Current A is pulling as an integer, Current B as a Float, and Current C and Current Average are showing 0. I am attaching the setup from System Management Console. Has anyone else encountered this issue? Volts mode is setup as 4W-WYE

[PV_DAQ]

I'm a generic Modbus guy, with no Schneider specific background.

Are you sure the master is not truncating Current A to an integer value/whole number?

Are you sure the master is polling Current C and Avg current? Lots of masters intializes holding registers (the tag for data it receives) to a value of zero. If not polled, the master register shows its initialized value of zero.

Generally, when a Modbus map states registers with the leading numeral 4, as in 43000 or 43002, the registers are generally one-based addressing, starting at 40001.

Zero-based addressing is typical of hexadecimal register addresses, or index-based addresses, indexed from 0000. The setup shows that zero-based addressing checked.

If you are using one based register numbers and mixing that with zero based numbering, you might be reading and interpreting the wrong set of registers. 32 bit floating point values require two adjactent registers, for instance Current B uses 43002 and 43003.

When attempting to read 43002 and 43003, you might be off by one and getting 43001 and 43002. The word/byte order changes when that happens, but I've seen where the resulting mixed-registeer value appear to be close to what it should be, yet be incorrect.

If it were me, I'd try disabling the zero based addressing function and then do whatever is necessary to try alternative word/byte orders until something reasonable appears and whether you get full FP values.

I'd also use a generic Modbus master like Modscan or Modpoll and see what the results are with the generic.

I'm not sure what register order means, but it might be the method of word/byte swapping to get the correct order to interpret a 32 bit floating point value.

I also do not understand register size = 5 digits? What's that? A Modbus register is 16 bits.

[Charles_Murison]

Hello @dice1010 ,

To expand on what PV_DAQ has said, have you tried to read the registers from the device with a modbus client other than the system you are using? https://www.se.com/ca/en/faqs/FA180037/ tester.exe for example or modbus poll, ModScan etc. The idea would be to poll registers to get the explicit 16 bit values (some modbus clients can convert these into 32 bit floating point values for you). The point is to very that device is responding to modbus polls as expected. There are also online tools that can help you convert hex numbers into floating point numbers https://www.h-schmidt.net/FloatConverter/IEEE754.html

regards,

Charles

[DanL · Accepted solution]

For information about Modbus register format and addressing, see the PM8000_Modbus_Map.xlsx file inside the firmware zip file.  ie. click on "PM8000 v4.0.0 Firmware and Associated Files (v4.0.0)" to download the zip file containing the documentation.
https://www.se.com/us/en/product-range/62252-powerlogic-pm8000-series/#software-and-firmware