clear tds 6604 waveform buffer

[oyester]

We are using labview 8.6 to drive a Tektronix tds 6604 scope via GPIB. We generate a pulse with user-defined characteristics, bounce it off the users DUT, and use the scope to capture the incident and reflected waveforms. We found when the scope wasn't triggering (for any one of a number of reasons) that the scope was still outputting waveforms. What is happening is, the scope is outputting the old contents of the waveform buffer, scaled to the current scope settings. Because the scope settings change each time, the signal returned by the scope changes each time (it gets multiplied by a different scale factor). So at first glance it looks like we are still acquiring data.

Our first thought was to clear the waveform buffer after each acquire. But it turns out that the tds 6604 does not have a clear waveform buffer command. We are working on some sample code to send to Tektronix; but, in the mean time. Does anyone have any ideas that we could try out?

[NathanT]

Hello Oyester,

      The first thing that comes to mind is that you could just read all of the data in the buffer and not use it, which would effectively clear it out.  You could also try to fix the root of the problem by changing how the scope is triggered in the first place.

Cheers,

NathanT

[oyester]

Thanks for your reply. Just for the record though, our problem is that reading from the waveform buffer does not clear the waveform buffer and the next time we read from it after a failed trigger event, we get the same data as before.We tried checking out the driver codes, but we kept running into protected CINs.

If we could find a way to poll the scope and ask it if it has triggered yet, that would work too. We just don't know how to do that.

[NathanT]

Hello Oyester,

        If your instrument driver is not made up of all native LabVIEW code, then I invite you to use the NI Certified LabVIEW Plug and Play (project-style) Instrument Driver for your instrument.  If you choose to use the LabVIEW Plug and Play Instrument Driver, you will be able to drill down into the SubVIs and see the specific commands that are being sent to the instrument.  Also, if an Instrument Driver is NI Certified, it is also most likely NI Supported.

         Please let us know when you have upgraded to using the NI Certified and NI Supported Instrument Driver.

Cheers,

NathanT