Hello,
I'm am testing an ad5235B-250 digital pot. I can write and read to the spi registers, and am powered by a clean 3.3V signal and the output pot is unloaded.
When I take an Ohm meter and measure across A to B on either port, the resistance value changes.
I expect it to read the same value (~250K) every time as it's fully unloaded.
For example, I program the port zero wiper to 0 using B10100000. I can read this back and confirm the write worked.
From a0 to b0 I get 187K (should be 250K). a to wiper is 183K, b to wiper is 100. So where did the 4K go?
Then I program the port zero wiper to 512 using B10100000. I can read this back and confirm the write worked.
From a0 to b0 I get 208Kohm (should be 250K). a to wiper is 105K, b to wiper is 108K. So this is 203K, it should be 208K (should be 250K).
Why is the a to b reading changing with programming, and why does a to wiper to b add up to something different than a to b?
s there something I'm doing wrong to make this thing stable?
Is there some reason a benchtop meter would be messing things up? Does it need a DC bias across the pot or something?
Thanks,
Dave.
