normalize routine in setMaxCurrent not working? about ina226 HOT 18 CLOSED

Thanks for reporting the issue, might take a few days

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Will start investigating today.

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No setup to test. Your analysis is looks correct.

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@morrowwm
Created a PR - see develop branch. Can you check this branch?

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It looks good. The current calculated by the INS226 is very close to that measured by my multimeter.

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Alternatively, what do you think of this approach to forcing current_LSB to be an integer, i.e. normalized?
INA226.cpp.txt

Starting at line 217, calculate calib, forcing no fractional part with round(). Then recalculate current_LSB using that calib.

This approach does not change the max current allowed as much.

Initial current_LSB:	0.00015259
Normalized current_LSB:	0.00015255 uA / bit
Max current:	5.00 A

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Then recalculate current_LSB using that calib.

why didn't I think of that!
Very good point as that way the internal variables stay way more consistent.

forcing current_LSB to be an integer

Would make sense to me if one could do the whole math in integer units.
Can you name some advantages?
I make a note in the future section in the readme,

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Just pushed a new version of .cpp file.

I added some #ifdef at the start of the function for switching on/off print statements.
furthermore it includes your suggestion to calculate current_LSB back from rounded calib.

give it a try.

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Doing all the math in integer will need more testing and I have so HW nearby (and enough time)
Note in readme to keep the thought

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give it a try.

I had to remove the old normalize lines, starting at about line 235. Then I defined printdebug and also added more digits to the _maxCurrent debug:

With normalize = false:

normalize:	 false
initial current_LSB:	0.00015259 uA / bit
factor:	1
Final current_LSB:	0.00015259 uA / bit
Calibration:	344
Max current:	5.00000000 A
Shunt:	0.09756356 ohm

BUS	SHUNT	CURRENT	POWER
6.984	-4.600	-47.150	331.879
6.986	-4.600	-47.150	331.879
6.986	-4.600	-47.150	331.879

And with normalize = true:

normalize:	 true
initial current_LSB:	0.00015259 uA / bit
Prescale current_LSB:	0.00015255 uA / bit
factor:	1
Final current_LSB:	0.00015255 uA / bit
Calibration:	344
Max current:	4.99889278 A <--- no longer 5.0, but an integer multiple of current_LSB
Shunt:	0.09756356 ohm

BUS	SHUNT	CURRENT	POWER
6.986	-4.603	-47.139	331.805
6.985	-4.600	-47.139	331.805

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So the new version works and still mayches your multimeter?

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So the new version works and still matches your multimeter?

Yes, it works well. Matches my multimeter to about 1 part in 400, both normalized and not.

I'll see if I can find a setup that will hold a stable, higher current and get more than three digits to measure.

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You might need to check the datasheet if you can get much better than 1 in 400 in terms of precission.

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You might need to check the datasheet if you can get much better than 1 in 400 in terms of precision.

The datasheet mentions several causes of small errors (see below) which in the end add up so a difference of 0.25% is not bad at all, given that most multimeters are in the 0.2% range themselves. You need a DMM with 0.02% or better to make better measurements (professional or lab equipment)

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@morrowwm
Are there other (serious) bugs that must be fixed?
Otherwise I merge this version and start a new branch for other issues if they appear.

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