I've been assigned the task of data logging the power consumption of our plant. We have a National Meter power analyzer 7000 v3 installed with modbus RTU protocol installed. I only know Power Basic and need help getting data from the power analyzer. The unit address is 10, register 04 contains the kilowatt usage I need. There is an RS-485 link used at 9600,n,8,1. Any help would be appreciated.

 

first of all i want to which plc r u using tell me about the plc then definately i could help u

 

I'm not using a PLC. The power analyzer will talk directly to an IBM PC via RS232/485 interface. The PC will store the data as daily files of the plants power consumption.

 

> I'm not using a PLC. The power analyzer will
>talk directly to an IBM PC via RS232/485
>interface. The PC will store the data as daily
>files of the plants power consumption.

In that case, its easy as pie. Easier even, its possible to screw up a pie. You just need to get a SCADA package on that computer with a modbus driver. If i was doing this project, and there were no other requirements for the computer, I would probably start by looking at National Instruments Lookout or Labview. You should be able ot get limited I/O packages from them on the cheap. As a matter o fact, i don't think you even need to buy a license unless you want more than 50 I/O. Just call them and tell them you want a trial version.

Oh, and in case you were looking for help with the modbus protocol, the address for the info in register 4 will most likely be 400005 (the number of zeros is kind of optional, you can have 3 or 4). For registers, you add 400001 to get the modbus address. On the off chance that it is treated like an analog input, the information will be in 300005 (not likely, but something to keep in mind if you cant find your data). And finally, some devices seem to start thier registers at 40000 and 30000, so you might find the info in 400004 or 300004.

If you have to do some bits later on, they are even easier. The address should be the same as the bit number.

-jeff