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ADC question (Read 234 times)

daveyK

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ADC question
Feb 24^th, 2009 at 6:22am

Hi All,

I was comparing the specs on the 3000 and 4000 series DSOs and have a question or two.

I understand that as more channels are deployed the resources of the ADC are reduced or divided by the number of channels in use.

Example:
The 3000 has a single ADC with a sample rate of 20 MS/s for 1 channel, 10 MS/S for 2 channels, and 5 MS/s for 3 or 4 channels.

The 4000 has dual ADCs with a sample rate of 80MS/s for 1 or 2 channels and 20MS/s for 3 or 4 channels.

Wouldn’t the sample rate on the 4000 for 3 or 4 channels be 40MS/s with dual 80 ADCs?

What am I not understanding??

Thanks,

dave

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Tom Roberts

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Re: ADC question
Reply #1 - Feb 24^th, 2009 at 8:43am

Dave,

Good question. Wink

A few details on why that is:

The 4423 has two 80MHz ADCs. A&B share one and C&D share the other.

When the ADC is shared it chop samples. In other words, it alternates taking a sample from one channel and then the other to build the two channels together across the screen.

There was a difficulty getting it to chop at 40MHz so it was reduced to 20MHz. This would be the maximum for one channel on the 3423.

Tom Roberts
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daveyK Super Nerd Picogroup Offline (Retired) - Elevation: 525 feet Posts: 2,357 Hellertown, PA, USA Pennsylvania USA Gender:	Re: ADC question Reply #2 - Feb 24^th, 2009 at 1:41pm Tom, Thanks for the explanation. Would that be a hardware limitation with the chop sampling at 40MS/s? Thanks, dave
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Tom Roberts Autonerdz Administrator Picogroup Offline Autonerdz Founder Posts: 8,598 Olympia Washington USA Gender:	Re: ADC question Reply #3 - Feb 24^th, 2009 at 2:00pm Dave, That's my impression but that's all the details I have.
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