Communication with process gas analyser


Thread Starter

Srinivas Duddu

I have to establish communication with a process gas analyser which supports MODBUS RTU. I tried the communication with MODTEST utility from M/s Daniel Europe Ltd. it works, but when i tried using MSCOMM control using VB, it does not work, what could be the problem ? Requesting reply from anyone out there!! Regards, srinivas duddu

Carl Burgess

I think the Daniels Modtest utility is written in VB, and uses the mscomm ocx, so that isn't the problem. Framing of RTU messages is time critical unlike modbus ASCII so my best guess is the problem lies in the way you've coded. You might want to post a little bit of your code here, and some details of the analyser.. Regards Carl Burgess

Kirk S. Hegwood

Could you use a zero speed indicator on the shaft or some other moving part. You would receive an contact closure when the speed reaches a certain range. Kirk S. Hegwood President Signing for Hegwood Electric Service, Inc. [email protected]

srinivas duddu

Thank U!! Pls. Find below the code sample i was working on In the MSComm Control i left the settings as commport:1 settings:9600,n,8,1 Handshaking: ComNone InBufferSize:1024 OutBufferSize:512 InputLength:7 DTR enable =TRue Private Sub CmdQuery_Click() MSComm1.Break = True MSComm1.CommPort = 1 MSComm1.PortOpen = True MSComm1.Output = "010300000001840A" MSComm1.InputMode = comInputModeText TxtResponse.Text = MSComm1.Input End Sub Using the Daniel Modtest utility i got the following response string from the analyser 01,03,02,03,C5,78,E7. I feel some problem is with the code, please advice / suggest any remedy in this regards by srinivas