ADC non-linearity on Q2686H

I’m trying to read ADC-AUX value using AT+ADC?. After several experiments with input DC voltage i found a great non-linearity in the beginign of the scale. True values appeares after 600-700mV. Does anybody knows what is it: bug or feature?

Sorry for my “broken english” :slight_smile:

How much do your measurements differ from what the ADC says?
The input impedance is listed as 1MegaOhm. I assume you have a signal setup such that the input impedance shouldn’t affect measurements.

Well, they differs significantly. For example, when we have 50mV on ADC input Wavecom returns 27mV. With smaller voltages Wavecom measurements rush to zero. Input signal comes from operational amplifire LM358 with 10KOhm output.

What version of the firmware are you using? ( ATI3 response? )

ATI3 response:
663_09gg.Q2686H 1955080 080207 16:01

You should talk to your distributor about this problem, and hope that they can get Wavecom to look into it.

It’s a bug that affects also Q24 “old family” and Q24xx “new family” and Q25 “dead engine”.
You may need to recalibrate the ADC (ask to Wavecom support) until the factories will fix the problem.
Since there was an overlap problem the performance still very poor: the reading is locked to ZERO approaching few millivolts.

Hope this can shed some light.

Our distributor promised to discuss this problem with Wavecom engineres as soon as they can.