Number of samples, Sample rates, timebase .....

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martinr
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Re: Number of samples, Sample rates, timebase .....

Post by martinr » Sat Apr 21, 2018 7:43 am

Autonerdz wrote:
After this little exercise, I feel I know my PicoScope a lot better than before.
Excellent. If you manage to duplicate the capture shown in my image above, you will learn a lot more.

I hope no one spoils your fun by telling you how it was done. :roll:
..no-one spoils my fun by telling me...? You probably got them all Googling as frantically as I was!

You know, I had missed the fact that you had used all 250M samples, whereas I had found that the max number of samples would be 100M. So I turned to Google and found a conversation between Martyn and francois at https://www.picotech.com/support/topic22051.html and I believe the way you would have utilised the full memory is best explained by 2 paragraphs in francios’ last post:
2/ Secondly, In order to reach the maximum sampling rate with the maximum time window the slow sampling mode must not be activated. This option is available in menu Tools > Preference > Sampling. We must take care that transition time scale is higher than the one intended to be used.
3/ The single trigger mode has to be activated otherwise the memory available is half what is possible.
Was slow sampling mode relevant to your case or did you just set for single trigger? And was that how it was done, anyway?

(I must now read up on slow sampling, too)

An intigued and grateful

Martin

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Autonerdz
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Re: Number of samples, Sample rates, timebase .....

Post by Autonerdz » Sat Apr 21, 2018 2:14 pm

Martin,

When you duplicate the capture you will know how it was set up.

You seem like the kind of guy that enjoys a challenge and will get the most out of the chase. I'm not gong to spoil that for you. Not many dive into the scope performance like you have and I am sure you will get more satisfaction and practice in the process. Enjoy 8)

martinr
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Re: Number of samples, Sample rates, timebase .....

Post by martinr » Sat Apr 21, 2018 8:03 pm

Autonerdz wrote:Martin,

When you duplicate the capture you will know how it was set up.

You seem like the kind of guy that enjoys a challenge and will get the most out of the chase. I'm not gong to spoil that for you. Not many dive into the scope performance like you have and I am sure you will get more satisfaction and practice in the process. Enjoy 8)
Thank you for your kind words and for not spoiling the fun. I won’t be able to replicate your CAN signal because my car is a 1996 pre-CAN, pre-OBDII vehicle, but I have a signal generator as well as a demo board given to me by most generously by Fluke Europe Technical Support that will do just as well. You are so right: I learn and remember things far better by finding out for myself, and no amount of reading or watching videos can provide those now-why-does-that-happen moments, which expose the gaps and cloudiness in one’s knowledge, and which only happen when one is left to make mistakes and discoveries and where finding the answer to one question raises another 2 questions along the way.

Martin

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Re: Number of samples, Sample rates, timebase .....

Post by martinr » Sun Apr 22, 2018 11:14 am

Done. When the total screen time is between 500ms and 500sec, provided the slow sampling transition time is set at a time longer than 500sec, and single trigger is also set, up to 250M samples can be obtained. In fact, with the setting at 500sec, I managed to see a total number of samples of 265M. with a sampling rate of 532kS/s and a sample interval of 1.88us. (With total screen time less than 500ms, the maximum sampling rate of 400MS/s is the determining factor as in normal streaming mode. And with times longer than 500sec, I found that the max number of samples was 100M, as in streaming mode.)

I noticed that with some of those longer screen times, a high frequency signal can be so dense that even zooming in as far as possible still isn't enough to show the detail.

I've also noticed that in the Properties column (I've set mine to show in Preferences), I believe where it says "No. samples" that should be "No. samples per channel". I'll send a report to Pico on that.

[I did try inserting an image from my Google Drive but I got the message "It was not possible to determine the dimensions of the image"]

All in all, a fascinating experiment and learning exercise.

Many thanks.

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Re: Number of samples, Sample rates, timebase .....

Post by Autonerdz » Mon Apr 23, 2018 4:18 pm

Very good. Glad you enjoyed that exercise. :D

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