Dual Channel Data Logging

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Bob Mehew
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Dual Channel Data Logging

Post by Bob Mehew »

I have just moved onto using both channels on my Pico ADC-200/100 and am rather confused. I set the time step at 10 micro seconds (or more precisely 10.24) and sought a fast block single set record of 32k samples. I anticipated that the resultant record would show a time step of 10 micro seconds and display only 16k samples on each channel. Whilst I am delighted to report that I got 32k samples from each channel, I am a little surprised that the time step doubled to 20 micro seconds. Is this correct or did I miss set something?

Also when using both channels, when does the device take a reading on each channel and is it at the same time? (It occurred to me that the doubling aspect may have resulted because say Channel A takes a reading at say 10 micro seconds and then Channel B at 20 micro seconds and then Channel A at 30 and so on, but reports them as both being taken at 20, 40 and so on micro seconds.) We am trying to compare the dynamic forces at both ends of a piece of rope and whilst we do see a difference in the data, some one has challenged us that part of the difference is due to the device not sampling both channels at the same time hence building in a delay.

ziko
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Re: Dual Channel Data Logging

Post by ziko »

Hi the ADC 200/100 has 2 ADCs, the clock is set at 50MHz. To get 100MS/s it uses both ADCs, in this mode you can only use one channel. If you enable both channels it will sample at 50MS/s for each channel.

By the way do you mean ns rather than us?

Hope this helps
Ziko

Technical Specialist

Bob Mehew
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Re: Dual Channel Data Logging

Post by Bob Mehew »

Thanks for the info. I did mean 10us and not ns. I got this curious doubling in timebase for 1280ns and 640ns as well. Checking with AC mains noise, the clock is not a factor of two out. A separate check on a pulse shows that both channels are sampling at the same time, even at 640ns timebase setting (times 2 of course). I just need to set a 5us timebase to get my desired 10us timebase.

ziko
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Re: Dual Channel Data Logging

Post by ziko »

Hi are you writing your own software or are you using PicoLog or PicoScope?

Kind regards
Ziko

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Bob Mehew
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Re: Dual Channel Data Logging

Post by Bob Mehew »

ziko wrote:Hi are you writing your own software or are you using PicoLog or PicoScope?

Kind regards
Picolog. see attached for example
100817 BPC 6 3.PLW
(372.67 KiB) Downloaded 529 times

Bob Mehew
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Re: Dual Channel Data Logging

Post by Bob Mehew »

sorry wrong sample, the previous was set at 10ns which gave 20ns time steps as you predicted. Attached is one set at 164ns but the recording shows 327ns.
Attachments
100725 home 09.PLW
(388.67 KiB) Downloaded 500 times

ziko
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Re: Dual Channel Data Logging

Post by ziko »

Hi I have managed to recreate your problem, there seems to be a bug in the software or driver. I have put this through to our software team who will be investigating this further.
Ziko

Technical Specialist

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