tektronix dpo 2000

[Hoard]

I am using the Labview tektronix DPO 2000 driver to read data from an oscilloscope.  I can easily fetch two channels of data, but they are not simultaneous samples.

The Get Multiple Waveforms routine actually downloads the channels one after the other, and the scope updates the data between scans.

How can I do something like pause the scope long enough to get two channels (1,250,000 samples each) that contain simultaneous data?

[Dennis_Knutson]

Why don't you try the example called Tektronix DPO MSO 2000 4000 Series Acquire Multiple Waveform Example? Your's does not configure either channel first. The Multiple Waveforms does in fact return the waveforms sequentially but if both channels are enabled, the actual acquisition will in fact be simultaneous.

[Hoard]

If you burrow into that example, you will find it defines an array of channels to read, and then reads one waveform at a time for each selected channel.  If the scope is running, the second waveform will have been taken later than the first and so on.

I need simultaneous samples.

Since posting, I found that you should be able to write ACQ:STATE:OFF, ON, RUN, or STOP and control the scope acquiisition.  I am about to go to the lab and try it.

[Dennis_Knutson]

If the scope is running, then it is misconfigured. If should be configured for a single acquisition - not continuous. The read multiple function calls the Initiate function only once and this is the only time the scope should be triggered.

And as I said, there is nothing you can do about the sequential transfer of waveforms.

[Hoard]

Sorry about the emoticons in the last note -- the auto feature changed them on me.

Should have been "ACQ:STATE:ON" or OFF.

I tried that and it works.

Now the remaining problem is that it takes 6440 msec to download two 1,250,000 element waveforms.  Now I need to look where the time is taken up.

[Dennis_Knutson]

There is a function in the driver that turns continuous acquisition on or off.

I believe the fetch is set to transfer data as binary but it is something that should be confirmed. If it is binary already, there is not much you can do. The 6 seconds works out to roughly 200 kb/sec which is not unreasonable for GPIB. The bus is slow.

[Albert.Geven]

The bus is faster but the instrument is slow?