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B2961A to simulate input to an ADC with varying Vref

Question asked by TestGuy on Aug 24, 2017
Latest reply on Aug 28, 2017 by TestGuy

We have a B2961A in the lab, and I was hoping to provide an input to an ADC circuit. Normally, the equipment under test provides an Excitation voltage, that a passive sensor turns into the signal to the ADC. This Excitation voltage is tied/ratiometric to the Vref of the ADC, so any change in the Excitation voltage is compensated.

When I use an external source like the B2961A, the input is not ratiometric to the Excitation volatge and therefore to Vref. So any change in Vref shows up as drift in the system, even with the B2961A being dead accurate and stable.

 

I was wondering if anyone has ran into a similar scenario and has found a solution.

 

I've only been able to come up with two, but both involve additional equipment (at least expensive ones), which we are hoping to avoid. But maybe it will spark other ideas.

 

1. Find a programmable (the whole idea is to automate this down the road) restive network. The problem is that we need 100000 individual steps. Not sure how hard that is to find.

 

2. Use a B2961B (2 Channels) or a second B2961A. In that case we could use 1 channel to provide the Vref to the ADC. The 2nd channel would provide the input to the ADC. However that would require modifications to the equipment under test, and we'd remove part of the circuit we are trying to test. I'd also have to look at how much maximum drift we'd get between the 2 channels of the B2961B. And of course we'd have to buy one...

 

Thoughts, ideas, hands slapping against foreheads?

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