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Topic: Voltage divider problem (Read 6 times) previous topic - next topic


dhenry


Read this http://hacking.majenko.co.uk/making-accurate-adc-readings-on-arduino


[/quote]Wrong![/quote]

That's an overly simplistic, black-and-white view of a highly complex world.

For example, I can point to multiple cases where the "wrong" approach is correct and the author's "Very nice. very elegant. And, more importantly, very useful." approach is "wrong".

What the author forgot to mention is that what's right or wrong is highly application specific so it is wrong to insist one approach is "wrong" while the others "right".

BillHo

Yes, the 1.1V have about 10% accuracy.
Quote
The spec sheet gives a nominal value of 1.1 volts, but states that it can vary from 1.0 to 1.2 volts. That means that any measurement of Vcc could be off by as much as 10%. Such a measurement could be less accurate than our power supply for the Arduino!


http://provideyourown.com/2012/secret-arduino-voltmeter-measure-battery-voltage/

tack

#18
Jan 02, 2013, 03:06 pm Last Edit: Jan 02, 2013, 03:10 pm by tack Reason: 1
How much more 'accurate' are you expecting things?

A couple of percent looks pretty good really. There are a number of things that are going to affect the readings you get between your multimeter and the analog ports via voltage divider.

Your Arduino analog ports have 8 bit resolution. Your multimeter most likely has better than 8 bit resolution.

Your multimeter has limits. It will have accuracy fingures given in both percentage and digits (if digital).

Your reference voltage may not be exactly 5v, and will vary slightly with the load on that supply line.

Your resistors have a tolerance. Are you using 5% or 1% resistors. They will also vary as they will have a temperature coefficient.

You are measuring the resistances too, which again will be within the measuring tolerances of your meter AND at a specific temperature that can change.

Combine all of these and what you are seeing is actually pretty good as far as I can see.

You're measuring with two different instruments, in different ways, with various things that have errors and tolerances.

Boopidoo

@tack
Well I'm almost pleased with the results but since there's more that can be one to improve the results I would like to try them as well.


Read this http://hacking.majenko.co.uk/making-accurate-adc-readings-on-arduino

That seems very interesting however I don't really undertand what that does so I guess I'll have to study it a little more.

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