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

Dave,

Good question.   ;)

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,

Thanks for the explanation.

Would that be a hardware limitation with the chop sampling at 40MS/s?

Thanks,

dave

Dave,

That's my impression but that's all the details I have.