Dual Channel Data Logging

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Bob Mehew
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Dual Channel Data Logging

Post by Bob Mehew » Mon Sep 06, 2010 5:46 pm

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 » Tue Sep 07, 2010 8:41 am

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

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Bob Mehew
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Re: Dual Channel Data Logging

Post by Bob Mehew » Wed Sep 08, 2010 11:18 am

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 » Fri Sep 10, 2010 3:37 pm

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 » Mon Sep 13, 2010 7:31 am

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

Kind regards


Picolog. see attached for example

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Bob Mehew
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Re: Dual Channel Data Logging

Post by Bob Mehew » Mon Sep 13, 2010 7:57 am

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.
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ziko
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Re: Dual Channel Data Logging

Post by ziko » Mon Sep 13, 2010 11:29 am

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

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