problem: not accurate measurement of battery using ADC

RE: problem: not accurate measurement of battery using ADC

haakonsh — Wed, 12 Jan 2022 08:51:58 GMT

Yes, along with Differential and Integral Non-Linearity, and temperature drift.

RE: problem: not accurate measurement of battery using ADC

alonmat — Tue, 11 Jan 2022 13:18:29 GMT

maybe the ADC itself cannot be more accurate.

the SADDC spec states that the error accuracy is +-3%.

Is it relevanbt to my case ?

RE: problem: not accurate measurement of battery using ADC

alonmat — Tue, 11 Jan 2022 09:30:49 GMT

I will try changing clock idea.

we measure with very low load. current is below 100uA

RE: problem: not accurate measurement of battery using ADC

haakonsh — Tue, 11 Jan 2022 09:27:06 GMT

You can try to run the HFXO while sampling, it should improve accuracy a bit.

btw, you're going to see a lot more than +/-10mV noise while running off a coin cell, all depending on the power load at the time of sampling and the state of charge of the coin cell.

RE: problem: not accurate measurement of battery using ADC

alonmat — Tue, 11 Jan 2022 09:13:46 GMT

The measurement changes in resolution of 1/100 volts and not millvolts.

We also perform test by connecting a voltage supplier instead of coin battery and we still have the same problem.

I suspect it i something in software side...

apis.mail.yahoo.com/.../thumbnail

RE: problem: not accurate measurement of battery using ADC

Otso Jousimaa — Mon, 10 Jan 2022 10:59:18 GMT

It looks like to me that you're already having accurate measurement with tens of millivolts as noise. The battery voltage will swing a lot more based on temperature and load.

The best thing I have done is to synchronize voltage measurement so that voltage is sampled after heavy activity, such as radio TX. The voltage will drop steeply at start, stay relatively flat for most of the device life time and will start to drop again when battery is nearing the end. I have not found a good formula to estimate remaining run time, but it's possible to give a "battery low" warning based on loaded voltage. You'll need to find your threshold for battery low at your temperature, load and battery model.