PicoScope 7 Automotive
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Limitation of waveform buffer memory
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ashtray1987
- OneWave
- Posts: 48
- Joined: Tue Jul 25, 2017 11:52 am
Limitation of waveform buffer memory
Hello all,
What is the limitation for the maximum number of waveform buffers with the Picoscope, is it related to the PC or is it a hardware limitation of the Picoscope 4425?
I ask because depending on the sample rate, my waveform buffer memory will reduce/increase.
As an example, I am currently monitoring 4 x 5V reference voltages on 4 x channels, my sample rate is 400kS and my timebase is 2s/div. With these settings I only get 62 previous waveform buffer memory, which is around 21 minutes before the scope will start to delete the oldest memory buffer.
Now for me there are frequent occasions where I need a higher sample rate than this, and would like to have a buffer that will run for much longer than 10mins or so, so that I can leave the Picoscope running and look at other vehicles.
I tried the same setup on another laptop, and the results were the same.
I ask therefore if it is possible to get a larger buffer if for example I have more RAM or whether this is purely a limitation of the scope itself.
Appreciate your feedback.
Thank you.
Ashley
What is the limitation for the maximum number of waveform buffers with the Picoscope, is it related to the PC or is it a hardware limitation of the Picoscope 4425?
I ask because depending on the sample rate, my waveform buffer memory will reduce/increase.
As an example, I am currently monitoring 4 x 5V reference voltages on 4 x channels, my sample rate is 400kS and my timebase is 2s/div. With these settings I only get 62 previous waveform buffer memory, which is around 21 minutes before the scope will start to delete the oldest memory buffer.
Now for me there are frequent occasions where I need a higher sample rate than this, and would like to have a buffer that will run for much longer than 10mins or so, so that I can leave the Picoscope running and look at other vehicles.
I tried the same setup on another laptop, and the results were the same.
I ask therefore if it is possible to get a larger buffer if for example I have more RAM or whether this is purely a limitation of the scope itself.
Appreciate your feedback.
Thank you.
Ashley
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Steve Smith
- Pico Staff Member
- Posts: 1587
- Joined: Sun Aug 25, 2013 7:22 am
Re: Limitation of waveform buffer memory
Hello Ashley, thank you for the post and sorry for my late reply
In a nutshell this depends upon how you are collecting the data you capture.
I will quote from this link https://www.picoauto.com/download/docum ... manual.pdf as it certainly sums up the difference between “Block Mode” and “Streaming Mode”
PicoScope 4000 Series Automotive Oscilloscopes run in various sampling modes. At
high sampling rates, the oscilloscope collects data much faster than a PC can read it.
To compensate for this, the oscilloscope stores a block of data in an internal memory
buffer, delaying transfer to the PC until the required number of data points have been
sampled. This is called block mode. At very low sampling rates, you may want to
switch to streaming mode. This allows data to be transferred back to the PC as it
is collected.
More on block mode
In block mode, the computer prompts a PicoScope 4000 Series Automotive
Oscilloscope to collect a block of data into its internal memory. When the oscilloscope
has collected the whole block, it will signal it is ready and transfer the whole block into
the computer memory via the USB port. The maximum number of samples in each
block depends upon the size of the oscilloscope's memory.
In your case Ashley the 4425 has an internal memory of 256 MB and this would be your limitation when capturing data below 200 ms/div.
200 ms/div is the setting within the PicoScope software where we transition from Block Mode to Streaming Mode. Streaming mode will be your collection mode at 2 s/div
You can change the transition point from Block Mode to Streaming Mode following the video below:
More on streaming mode
In streaming mode, the computer prompts the PicoScope 4000 Series Automotive
Oscilloscope to start collecting data. The data is then transferred back to the PC
without being stored in oscilloscope memory. Data can be sampled with a period of
between 1 ms and 60 s, and the maximum number of samples is limited only by the
amount of free space on the PC's hard disk.
In your case Ashley the limitation when capturing above 200 ms/div is governed by the software at 100 MB (All the above therefore impact on the size of your waveform buffer)
I guess we have a number of options to achieve what it is you are looking for:
If we reduce the sample rate we can increase the number of waveform buffers but this is not always desirable (depending on what you wish to capture)
With your example of 4 x 5 V reference voltages we could utilise Triggers, Masks and Alarms to either capture the event you are looking for or, to automatically save all your waveform buffers, followed by an automatic restart of captures.
There is however the chance that during the auto save and recapture of buffers we could miss the glitch you are looking for! Therefore I think a Mask Fail would be more relevant.
If you could post a psdata file of a typical failure for the 5 V ref supply then we can create a Mask and re-post it here for viewing/sharing.
On another note, PicoLog version 6.1.8 https://www.picotech.com/downloads will function with the 4425 PicoScope but the sample rate is limited to 1 KS/s
I hope this helps and please feedback when you can for any clarification.
Take care…….Steve
In a nutshell this depends upon how you are collecting the data you capture.
I will quote from this link https://www.picoauto.com/download/docum ... manual.pdf as it certainly sums up the difference between “Block Mode” and “Streaming Mode”
PicoScope 4000 Series Automotive Oscilloscopes run in various sampling modes. At
high sampling rates, the oscilloscope collects data much faster than a PC can read it.
To compensate for this, the oscilloscope stores a block of data in an internal memory
buffer, delaying transfer to the PC until the required number of data points have been
sampled. This is called block mode. At very low sampling rates, you may want to
switch to streaming mode. This allows data to be transferred back to the PC as it
is collected.
More on block mode
In block mode, the computer prompts a PicoScope 4000 Series Automotive
Oscilloscope to collect a block of data into its internal memory. When the oscilloscope
has collected the whole block, it will signal it is ready and transfer the whole block into
the computer memory via the USB port. The maximum number of samples in each
block depends upon the size of the oscilloscope's memory.
In your case Ashley the 4425 has an internal memory of 256 MB and this would be your limitation when capturing data below 200 ms/div.
200 ms/div is the setting within the PicoScope software where we transition from Block Mode to Streaming Mode. Streaming mode will be your collection mode at 2 s/div
You can change the transition point from Block Mode to Streaming Mode following the video below:
More on streaming mode
In streaming mode, the computer prompts the PicoScope 4000 Series Automotive
Oscilloscope to start collecting data. The data is then transferred back to the PC
without being stored in oscilloscope memory. Data can be sampled with a period of
between 1 ms and 60 s, and the maximum number of samples is limited only by the
amount of free space on the PC's hard disk.
In your case Ashley the limitation when capturing above 200 ms/div is governed by the software at 100 MB (All the above therefore impact on the size of your waveform buffer)
I guess we have a number of options to achieve what it is you are looking for:
If we reduce the sample rate we can increase the number of waveform buffers but this is not always desirable (depending on what you wish to capture)
With your example of 4 x 5 V reference voltages we could utilise Triggers, Masks and Alarms to either capture the event you are looking for or, to automatically save all your waveform buffers, followed by an automatic restart of captures.
There is however the chance that during the auto save and recapture of buffers we could miss the glitch you are looking for! Therefore I think a Mask Fail would be more relevant.
If you could post a psdata file of a typical failure for the 5 V ref supply then we can create a Mask and re-post it here for viewing/sharing.
On another note, PicoLog version 6.1.8 https://www.picotech.com/downloads will function with the 4425 PicoScope but the sample rate is limited to 1 KS/s
I hope this helps and please feedback when you can for any clarification.
Take care…….Steve
Re: Limitation of waveform buffer memory
So in this world where memory is virtually free of charge (well relatively at least) why on earth did you put in a tiny 256mb one instead of something "usefull"?
Re: Limitation of waveform buffer memory
Hello,
I will upload the crash report from waveform buffer memory,if the CAN decoding is enabled the PICO crash every time,if not then I can store more than 70 frames in memory buffer.
Best regards
I will upload the crash report from waveform buffer memory,if the CAN decoding is enabled the PICO crash every time,if not then I can store more than 70 frames in memory buffer.
Best regards
- Attachments
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- Report_2019_01_28.zip
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Steve Smith
- Pico Staff Member
- Posts: 1587
- Joined: Sun Aug 25, 2013 7:22 am
Re: Limitation of waveform buffer memory
Hello and thank you for the feedback.
Rest assured all comments will be forwarded onto the software/hardware teams via our reporting system and new feature requests such as memory limitations will be reviewed.
The crash has been rectified Victor and we are testing a "Release Candidate" version as we speak.
Thank you again, take care......Steve
Rest assured all comments will be forwarded onto the software/hardware teams via our reporting system and new feature requests such as memory limitations will be reviewed.
The crash has been rectified Victor and we are testing a "Release Candidate" version as we speak.
Thank you again, take care......Steve
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ashtray1987
- OneWave
- Posts: 48
- Joined: Tue Jul 25, 2017 11:52 am
Re: Limitation of waveform buffer memory
Hello Steve,
Thank you very much for your detailed feedback as always.
Is there any oscilloscopes on the Picotech side of the company that offer a higher buffer memory, i.e. the 8 channel 20mhz scopes?
Thank you.
Ashley
Thank you very much for your detailed feedback as always.
Is there any oscilloscopes on the Picotech side of the company that offer a higher buffer memory, i.e. the 8 channel 20mhz scopes?
Thank you.
Ashley
Re: Limitation of waveform buffer memory
Hi Ashley,
Ii’m grateful for your question because Steve’s explanation of the 2 sampling modes has helped me finally clear a bit of a mental block.
“Block mode” and “streaming mode” to me are more descriptive than fast/normal sampling and slow sampling, especially after reading the reasons for block mode.
I previously asked a question not unrelated. I wonder if any of the answers help you?
topic19921.html?&p=89561#p89561
Martin
Ii’m grateful for your question because Steve’s explanation of the 2 sampling modes has helped me finally clear a bit of a mental block.
“Block mode” and “streaming mode” to me are more descriptive than fast/normal sampling and slow sampling, especially after reading the reasons for block mode.
I previously asked a question not unrelated. I wonder if any of the answers help you?
topic19921.html?&p=89561#p89561
Martin
Re: Limitation of waveform buffer memory
Hello,Steve Smith wrote: ↑Thu Feb 07, 2019 11:55 am
The crash has been rectified Victor and we are testing a "Release Candidate" version as we speak.
Some good news about the improved version?
Will be available an"automotive brother" of Pico 5442D MSO?
Thank you