Hi,
I am trialling a setup where we will interogate a Krohne Flow meter via modbus rather than pulse outputs. The modbus setup should allow for us to collect flow rates as well as the accumulating total and avoid inconsistancies that we see when reading pulses only.
The issue I have is that the Krohne IFC 050 signal converter is presenting the Counter data as double float..
I cant seem to get this to show in any sensible format with either a modbus test tool (modbusmat1.1) or with a cr1000x.
My Questions are...
Has anyone had any success in reading double float registers with the modbusmaster instruction? If so what is the strategy..
Second then is it possible?
and finally I see on the CR1000x that the control ports can be configured with the serial open function to be RS485, so I can use this to connect the signal converter directly? (not tested yet) currently using a rs232 to 485 converter from the rs232 port on the logger
the Krhone manual is here..
http://www.manualsdir.com/manuals/368267/krohne-ifc-050-converter-modbus-en.html, p12 for the register options
any ideas much appreciated
regards
Paul
The CR1000X does support variables declared as Double. The ModbusMaster instruction does not have direct support for the data format.
Read the value in as two variables in ABCD byte order. Then use MoveBytes to do a binary copy from those variables into a variable declared as Double. Check the manual for the device, to check if you need to change the byte order. Changing the byte order can be done by using MoveBytes multiple times, one byte at a time.
Public LargeNumber As Double
Public SinglePrecision(2) As Float
Public ModbusResult As Long
BeginProg
Scan (1,Sec,0,0)
ModbusMaster (ModbusResult,ComC1,9600,1,3,SinglePrecision(),1,2,3,100,2)
MoveBytes (LargeNumber,0,SinglePrecision(),0,8)
NextScan
EndProg
Yes, with a CR1000X and a CR6 you do NOT need a RS-485 converter. Can be done directly with C Pair. You will need to setup the pair in DevConfig to do this.
excellent, thx both. was looking down the path of reading them in 2 sections but the float conversion, math and modbus format was doing my head in... good to see CSI 1 step ahead again..
much appreciated for code and strategy
cheers
Paul
Ok.. I now have a successful code working in a test environment on a CR1000x.. took some head scratching and setting changes on the Krohne but I now have it resolving the count totals correctly. working in Big Endian output from the Meter.
the CR1000x code bits are..
Public ModbusCNT(2) As Float
Public LargeNumber As Double
..
ModbusMaster (Mod_Result,ComRS232,19200,1,4,ModbusCNT(),9,2,3,100,2)
MoveBytes (LargeNumber,0,ModbusCNT(1),0,8)
MoveBytes (LargeNumber,9,ModbusCNT(2),0,8)
and get this returned for a counter total of 706.467
ModbusCNT1 4.189909
ModbusCNT2 -6.912387e+13
LargeNumber 706.467205967539
now..
I was wanting to deploy a CR300 cell 200 for this monitoring project so I am now testing the Flow meter with this platform
same code
Public ModbusCNT(2) As Float
Public MeterCount1 As Double
ModbusMaster (Mod_Result,ComRS232,19200,1,4,ModbusCNT(),9,2,3,100,2)
MoveBytes (MeterCount1,0,ModbusCNT(1),0,8)
MoveBytes (MeterCount1,9,ModbusCNT(2),0,8)
once again for the Counter total on the flow meter of 706.467 i get these numbers
ModbusCNT(1) 4.189909
ModbusCNT(2) -6.912387e+13
but now the Double foramtted number is
MeterCount1 -4.03232949058767e+108
Any ideas why this is?
the source modbus format is consistant over both the CR1000x and CR300 but looks like either the moveBytes or application of the double format is operating differently in the cr300
I havent found anything in the help files so any assistance much appreciated
regards
Paul
The CR300 datalogger is little endian, and the CR1000X is big endian. So, on the CR300 you need to move bytes differently.
Thanks JDavis,
I was able to change output from the flow meter to little endian and with subtle change to the modbus request all is now gold..
much appreciated
This post is under review.