Power Module Voltage Calibration

I currently use the power Module: https://emlid.com/shop/power-module/
In the documentation i found the description (https://docs.emlid.com/navio2/Navio-dev/adc/):
A0 - board voltage (shows 5V)
A1 - servo rail voltage
A2 - power module voltage (ADC0, POWER port)
A3 - power module current (ADC1, POWER port)
A4 - ADC2 (ADC port)
A5 - ADC3 (ADC port)

What is the correct scaling of A2 and A3? Do I have to calibrate myself? For the voltage I can do, but not for the current.
Can someone help me here?

Hello Flavio,

First you need to calibrate your voltage sensor with a precise multi-meter or battery tester and at the
same time you fill the field “Measured battery voltage” in Mission Planner with your measured value.

Then you assign a value, let’s say 18, to “Amperes per volt”. You charge your battery at 100%
and you make a long hover flight like 10 minutes. Longer your flight is more accurate will be your
measure. After landing you download the DataFlash Log from Mission Planner and you read the
maximum CURR.CurrTot showed in the Log Browser on the graph at the end of the flight.
You charge you battery again at 100% and you check how many mAh the charger has filled in it,
then you’ll compute the new “Ampere per vol”.

Example: Your first try for “Amperes per volt” = 18, your CURR.CurrTot shows 3000mAh and your
charger filled 3300mAh, your new and right “Amperes per volt” will be 18x3300/3000=19.8

You make this procedure again to check or adjust your value and you save your parameters.

With this method I achieve measurement accurate better than 97% without the need of any ampere
meter and/or static charge. Furthermore even if you would measure the amperage when connecting
a static charge the reading is not stable and not accurate enough.

Hope this helps…

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