Announcement

Collapse
No announcement yet.

CMore Waveform Capturing

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts


  • CMore Waveform Capturing

    Hi All,

    I was wondering if anyone knew of a good solution to display a 24VDC waveform on the CMore platform? I have a 24VDC speed pickup prox with aprox 50% duty cycle running at 750Hz. Operations would like to see the waveform of the sensor on our CMore screen. We are running on Rockwell's CompactLogix platform using ethernet for comms. Any advise would be appreciated!

    Regards,
    Joe


  • #2
    One can buy a nice digital 'scope for a lot less than a C-More, I understand that you already have the C-More, but I can't think of any practical way to do what you want. The C-More has limited charting capability, pretty much only the trend line chart. I suppose IF the PLC' and its ADC was fast enough (I'd be surprised if it was) one could fill an array on the PLC then using a tag trigger shift it onto a trend line, but it would be a pain and probably wouldn't work anyway.
    I'm not sure what part of the "waveform" you want to see, but the Nyquist frequency for 750Hz is 1500Hz (666uS sample time, pretty quick for most PLCs) and that only gets you the 750Hz fundamental, to get any significant detail of the "waveform" you need to sample quite a bit faster.

    Comment



    • #3
      Originally posted by Tinker View Post
      One can buy a nice digital 'scope for a lot less than a C-More, I understand that you already have the C-More, but I can't think of any practical way to do what you want. The C-More has limited charting capability, pretty much only the trend line chart. I suppose IF the PLC' and its ADC was fast enough (I'd be surprised if it was) one could fill an array on the PLC then using a tag trigger shift it onto a trend line, but it would be a pain and probably wouldn't work anyway.
      I'm not sure what part of the "waveform" you want to see, but the Nyquist frequency for 750Hz is 1500Hz (666uS sample time, pretty quick for most PLCs) and that only gets you the 750Hz fundamental, to get any significant detail of the "waveform" you need to sample quite a bit faster.
      I tried this years ago, with a significantly lower sample frequency, and your suspicions described above were true then, too.
      I had issues with waveform sync and whether or not parts of the wave were rendered on the screen.
      I was capturing and (later, by user selection) trying to display a 'graph' of the volt/current charge curves for multiple capacitors (under test.)
      Sometimes it would work wonderfully (albeit SLOWLY) and sometimes the waveform was just botched. Same code, same graph, just unreliable.
      Granted, the firmware that I was using at the time may have been the issue. dunno. I was using PAC Suit v1.4.1(1) and probably CMORE v 2.72(?)

      Comment

      Working...
      X