Analog shield DAC off set

[a.honarfar]

Hi Friends,

We are using the analog shield for measuring some analog feedbacks but we find out there is 0.65V off set for each reading chanels and also the open circuit voltage is 2V. Can you tell us what is wring in there?

[JColvin]

Hi a.honarfar,

The open circuit voltage you are observing on the ADC is the voltage reference of 2.048V (see page 3 of the schematic). Similarly, there will be a open circuit voltage on the DAC of approximately -5V. I'm looking to see if I also observe any offset in my setup now; I'll get back to you in a bit.

Thanks,
JColvin

[JColvin]

Hello again,

I am also getting some different values than I expect to be seeing in terms of voltage. They aren't an offset in the true sense (I'm getting a more negative value than expected when producing negative voltages and a more positive value than expected when producing positive voltages). I'll continue looking to see what I can find.

Thanks,
JColvin

[JColvin]

Hello,

I'm uncertain as to why you are seeing such a large offset. I check various output voltages and resistance values on my board and checked them with the datasheet to find (not surprisingly) that there is variance between the reported value and the observed value, which (at least for reference voltages) can produce some values that are slightly off. However, the most variance I observed over the full voltage range was 0.03V, and that was at the extremes of the voltage range (-5 and +5V). The variance steadily decreased as I approached 0V. So I'm not sure as to why you are seeing a 0.65V offset. I presume you are using some of the example code (like the ramp example) to observe this offset?

Thanks,
JColvin