Accuracy of inbuilt ADC - pretty good with oversampling

Hardware
#1

The MCP3424 ADC suggested in another thread is giving very accurate results. It’s in total agreement with my Fluke 77 which is only good to three decimal places.

In a bake-off between the MCP3424 and the Imp’s ADC, the Imp with oversampling was better than I expected. Vdd and Vdda were slightly over 5v so the Imp’s reading were likewise slightly high.

Bottom line; a separate voltage reference to Vdda and oversampling and the Imp’s ADC is quite respectable. Of course it’s slow with oversampling, not differential and takes one pin per input but it could save on an external component.

Imp_ADC.png713×407

#2

The scale on the left is mV.

#3

Not bad! Which imp? The imp001 has issues in that power and ground go via a connector, hence when the imp draws current this can both scale and offset the ADC reading.

Solder-down imps are better in that regard.

#4

It’s an imp001. I’ve some Imp002 bare boards coming, hopefully I can solder them (no SMD experience) and I’ll test the ADC.