Logomatic V2: ADC inequties...

I tried letting the logomatic run in the analog mode at various frequencies and did find that for Frequencies <10 a leading zero must be used.


Next, with nothing connected to the ADC pads, I let the Logomatic run long enough for about 65,000 lines of values to be written. Then I averaged the logged values and that result came out to:

Average of AD1.3 = 545.7590143

Average of AD0.3 = 577.1797818

Average of AD0.2 = 505.1089647

Average of AD0.1 = 508.3867552

Average of AD1.2 = 641.2651102

Average of AD0.4 = 761.6829328

Average of AD1.7 = 207.3474174

Average of AD1.6 = 235.1309377

I repeated this procedure several times and the results were roughly the same.

I do realize that the open pads are measuring the random, stray voltage in the air, but why is the averaged value AD0.4 significantly higher, and why are the values of AD1.7 and AD1.6 significantly lower?

Inadequate board cleaning leaving some flux on the board? It can be conductive.

Leon

If the pads are board mounted, then they will pick up RF noise.