LeCroy Wave Series - LabVIEW driver bug

[BapD]

Hi fellow LV users,

I found a little bug in some Lecroy scope LV driver found there : 

http://sine.ni.com/apps/utf8/niid_web_display.download_page?p_id_guid=07C0AC709BD14C10E0440003BA7CCD...

Version 3.3 at the moment.

I can't find how to report it so I am doing it here.

The bug is due to the fact that these instruments (I am working with an HDO6104) work by digitizing all four channels sequentially. Hence the samples of all channels are not aligned in time.

However the driver as it's made does not take care of that. When waveforms are requested, they are all aligned starting at a blank t0.

You can easily reproduce the bug by digitizing the same 100 MHz sine on all channels: you'll obtain 4 waveforms not in phase because the different t0 are not included in the waveforms.

The fix is really easy because the information is readily available however it just wasn't wired to the t0 terminal of the build waveform...

Open "Fetch Waveform.vi"

- remove the blank timestamp wired to the t0 terminal.

- wire the "horizontal offset" output of "Get Descriptor.vi" through a "To Timestamp" to the t0 terminal of the build waveform block.

Then make sure your subsequent code care about that t0 value...

Bugged:

Fixed:

Regards,

Baptiste

[santo_13]

Good job, you saved others folks a good chunk of time debugging why they don't get the waveform timing right.

To make it easier for other folks to find this thread, please add more tags (like models supported by the driver etc.,) and mark the post as a solution. BTW, you've posted the snippet in 2020, I would recommend saving only the VI to modify in LV 2016 (or any earliest possible version) and attach to the post so that the fellow forum members just need to replace the VI instead of editing them.

[Albert.Geven]

As a suggestion: Also send this to instrument.drivers@ni.com

They should be watching these threads also but maybe miss it.

It is sufficient to send the link and ask how they can help to update the official driver page.

[alanjb]

Hello Baptiste - Thanks for sharing this, I can get the driver updated, probably next month. Please let me know if you have any other issues, at alan.blankman@teledyne.com

Best Regards, Alan

[alanjb]

Hello Baptiste, and everyone else,

After making the change suggested above, what else needs to change so that the waveform graph shows T=0 as the location of the trigger point (which is what wiring in the horizontal offset should do). 

Thanks,

Alan

[BapD]

Hi,

t=0 is the time when the scope triggered

t=t0 is the time when the first point was sampled (t0 is different for each waveform)

So you have nothing to change on the graph to show the triggering moment at zero.

However you have to uncheck the box "Ignore waveform time stamp on x-axes" on the "Scales" tab to NOT have the waveforms start at zero, but at t0 instead.

[edit] For cosmetic reasons you might also want to change back the X scale formating to something like floating point instead of a full format absolute date.

Baptiste

[alanjb]

Got it! Thanks Batiste!

BTW I'll be submitting a new version of the driver this week that includes your change + one or two more. I'll post here when it hits the NI website. If you are interested in getting it sooner, please email me at the address in my sig.

Best Regards,

Alan

[BapD]

I am fine waiting for the official release 🙂

Great to see that a driver is maintained and that user feedback is taken into account 👍

Regards,

Baptiste