Sigma Delta Non-Linear

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BeS__284136
Level 3
Level 3
5 sign-ins 10 replies posted 5 replies posted

I am having some issues with non-linear and inconsistent readings off the Sigma Delta converter.

   

My circuit uses a resistor ladder to attenuate a high DC voltage. That is buffered with an INA217 amplifier. The readings off the amplfier measure in a near linear fashion.

   

I am having a problem with the converter. It always reads a few milliviolts below what my meter reads. This variation changes with different voltage readings, especially over a large range.

   

The amplifier circuit is pretty linear, so it is safe to say the problem is the converter.

   

I read about a similar problem on another thread regarding analog routing and the voltage reference. I have the converter set:

   

Range 0-1.024V

   

Internal 1.024V reference.

   

16 bits at 48ksps.

   

What is going on?

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