Test and Measurement Forum

Dual Channel Data Logging

Post any questions you may have about our current range of USB data loggers

Dual Channel Data Logging

Postby 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.
Bob Mehew
Active User
Active User
 
Posts: 6
Joined: Tue Jun 16, 2009 10:07 am
Location: Southport

Re: Dual Channel Data Logging

Postby 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

Technical Specialist
ziko
Zen Master
Zen Master
 
Posts: 1705
Joined: Fri Dec 01, 2006 10:03 am
Location: St Neots

Re: Dual Channel Data Logging

Postby 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.
Bob Mehew
Active User
Active User
 
Posts: 6
Joined: Tue Jun 16, 2009 10:07 am
Location: Southport

Re: Dual Channel Data Logging

Postby 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

Technical Specialist
ziko
Zen Master
Zen Master
 
Posts: 1705
Joined: Fri Dec 01, 2006 10:03 am
Location: St Neots

Re: Dual Channel Data Logging

Postby 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
100817 BPC 6 3.PLW
(372.67 KiB) Downloaded 131 times
Bob Mehew
Active User
Active User
 
Posts: 6
Joined: Tue Jun 16, 2009 10:07 am
Location: Southport

Re: Dual Channel Data Logging

Postby 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.
Attachments
100725 home 09.PLW
(388.67 KiB) Downloaded 108 times
Bob Mehew
Active User
Active User
 
Posts: 6
Joined: Tue Jun 16, 2009 10:07 am
Location: Southport

Re: Dual Channel Data Logging

Postby 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

Technical Specialist
ziko
Zen Master
Zen Master
 
Posts: 1705
Joined: Fri Dec 01, 2006 10:03 am
Location: St Neots


Return to USB PC Data Loggers

Who is online

Users browsing this forum: No registered users and 0 guests