Time offset?

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justindavis
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Time offset?

Post by justindavis » Thu Feb 07, 2013 4:14 pm

Is there a way in software to do a time offset for one channel relative to the others to adjust for things like difference in cable lengths or skew in trace lengths? Or with the reference waveforms? Sometimes the sampled data has a slight delay relative to my reference waveforms. Perhaps with the math channels?

Thanks,

Justin

Martyn
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Re: Time offset?

Post by Martyn » Fri Feb 08, 2013 7:08 am

You can't do it with channels but you can with reference waveforms.

Select the reference waveform and make it visible, find the x1.0 button at the bottom right or left of the screen associated to the reference trace, and click on it to locate the delay feature.
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Mark_O
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Re: Time offset?

Post by Mark_O » Fri Jun 19, 2015 10:14 am

Martyn wrote:You can't do it with channels but you can with reference waveforms.
It's unfortunate, but it seems like the deeper I look into the Picoscope capabilities, the more limitations I uncover. :oops:

This capability is completely routine, even on the cheapest of standalone DSOs, where it is commonly referred to as "Channel Deskew", or "Delay Calibration". It's not at all uncommon to have to trim this setting, to bring all the active channels into time alignment. Only it's not possible at all on any Picoscope? Has the situation changed since Justin asked this question, 2 years ago?

This seems like a surprising limitation, since it is purely a Display characteristic (and already provided for Reference waveforms). I'd really like to see this capability added, possibly also as another Attribute of a Probe. Especially when evaluating pulses, temporal windowing, and logic states between 2 channels, this can be an important factor. :!:

- Mark
Last edited by Mark_O on Fri Jun 19, 2015 8:55 pm, edited 1 time in total.

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Re: Time offset?

Post by Mark_O » Fri Jun 19, 2015 10:36 am

Well, to be fair, and having given it more thought, perhaps it's not quite as important as I've made it out to be. Most ranges of PicoScopes don't sample beyond 1 GSa/sec, which is 1 ns per sample. You'd need ~25 cm of lead-length difference to shift things by one sample interval. Which you could correct just by using more closely matched test leads.

I would think this might be of some concern to those with ps6000's, sampling at 5 GSa/s, though. Or a ps9000, sampling at 20 GHz. Though your Pico Oscilloscope Range-web page says "Max Sampling 1 MS/s" in the box for that model! :oops:

- Mark

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Re: Time offset?

Post by Martyn » Fri Jun 19, 2015 1:40 pm

You can deskew by creating a maths channel
Advance/Delay. Add [t] after a channel name to advance it by t seconds. For example, A[0.001] is equal to Channel A advanced by 1 millisecond, and A[–0.001] is equal to Channel A delayed by 1 millisecond.
For information the 9000 series are sampling scopes, not real time scopes, the same rules do not apply and the software is completely different.
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Re: Time offset?

Post by Mark_O » Fri Jun 19, 2015 2:22 pm

Good point about the 9000-series, Martyn. Thanks for that. That's way outside my pay-grade, so I've never paid much attention to it. :) I was just looking for anything sub-nanosecond.

Very interesting that a Maths channel can offset time, and not just an amplitude value. Certainly very flexible! But creating a redundant parallel channel just to fix a nanosec or two seems like a stretch. Now that you've pointed it out, I did find it in the Manual. But I looked pretty carefully beforehand, and never found it on my own.

Doesn't this become more of an issue though with something like the MSO models? I.e., the propagation delays are going to be quite different if you're probing the same signals in both digital and analog domains, yet you'd certainly want them to be in sync. Or do the PicoScopes compensate for that differential internally?

- Mark

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Re: Time offset?

Post by sbabic44 » Sun Dec 17, 2017 11:48 am

Hello and sorry for reviving an old thread, but it seemed more appropriate than opening a new one!

As far as I know channel deskew still doesn't exist. It is a fundamental feature, and it has no place in math channels. It is something routinely used with current probes for instance, and in a perfect world would be part of probe definition. Capability to create custom probes was a big factor for me to decide to get Picoscope, and was extremely disappointed when I realized there is no channel deskew. I didn't even check if it's there, as I presumed it would be.. 250€ scopes have it. 2000€ Picoscope should too..
That is very important when doing power analysis on mosfet switching and such. These are nanosecond scale events, and need to be calibrated /aligned precisely... Inherent 2ns typical channel to channel on 3406D is ok but probes can have lots more (it can be 15 nsec, it can be 60 nsec )..

With math channels and deskew built in probe definition , 4ch picoscope would be my first choice for power analysis. Now, not so much..

Thanks and best regards,

Sinisa

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Re: Time offset?

Post by Martyn » Mon Dec 18, 2017 9:50 am

This has not been added yet, but I will flag your request to the development team.
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Re: Time offset?

Post by sbabic44 » Mon Dec 18, 2017 4:20 pm

Martyn wrote:This has not been added yet, but I will flag your request to the development team.
I appreciate it, thank you very much for great support..
If any help with testing or working out details is needed I'm willing to help with that as much as I can..
Best regards,
Sinisa.

Dumle
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Re: Time offset?

Post by Dumle » Tue Apr 10, 2018 12:56 pm

I also need to delay one channel. Have a load cell connected to one channel and a position sensor connected to the other. Unfortunately the load cell delays the output signal by 12ms so my speed/force diagram doesn't look right. (have a 2000-series)

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Re: Time offset?

Post by Martyn » Tue Apr 17, 2018 7:07 am

We have added your name to the feature request
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KonstantinM
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Re: Time offset?

Post by KonstantinM » Mon Jul 02, 2018 6:13 pm

I use PicoScope 3425 with software ver.6.12.7.2687 for 50Hz AC voltages and current measurements. For my current sensors I created "custom probes" with necessary scaling and units conversion. During analysis of measured waveforms I understood that current sensor gives signal with leading angle, and after googling for it's characteristics I found a confirmation that 4 degrees leading angle should be compensated during measurements. First surprize was that there is no such setting in "Custom probe" dialog. I carefully read the help file and found out that delay is possible to set for Math Channel: "Advance/Delay. To deskew a signal, select the channel and add the deskew time in seconds, in square brackets. For example, to advance Channel A by 1 millisecond, enter A[0.001], and to delay Channel A by 1 millisecond, enter A[–0.001]".
The second surprize is that Math wizard can't understand A[–0.001] equation. It writes an "Invalid formula" error for any negative figure inside [] brackets. But even if I write any positive value like A[0.005] - absolutely nothing changes for this math channel - it looks absolutely like original "A" without any advance.
The only way I found by now is use of "Reference waveform" with 0,22 ms delay - but it's really annoying and stupid activity when analyzing dozens or hundreds of measured signals.
Please advice how to implement a delay for custom probe?

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Re: Time offset?

Post by Martyn » Fri Jul 06, 2018 7:59 am

Can you email a psdata file to support@picotech.com so that we can look at your data and settings
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