Electronics > Projects, Designs, and Technical Stuff
Measuring wide range current draw of micropower applications
Amper:
Well thats embarrassing, usually i search before posting...
Thank you for the links however, some of the stuff is very interesting.
magic:
Without reading those other threads I would say:
Use a few ohm shunt to maintain reasonably low burden voltage at full load and provide as many parallel amplifier-ADC paths with different gains as you need. That's probably going to be 2, and only the low gain one needs to be fast and only the high gain one needs µV precision, which isn't even the worst situation it could be.
Say, ATtiny13 + trimmed OP07 + dunno, maybe even NE5534?, whacked together on a perfboard.
Amper:
Yes, thats one of the considerations ^^
Having 1V drop@ 20mA would give me a 50Ohm shunt, .3mV@ 6uA. Not really any problem but in this case building the auto ranging shunt would not be so much more of a work.
SiliconWizard:
--- Quote from: Amper on October 31, 2019, 07:51:04 am ---Well thats embarrassing, usually i search before posting...
Thank you for the links however, some of the stuff is very interesting.
--- End quote ---
There are probably yet others. But no problem, that happens to everyone. This is actually a recurring topic, as it's a very serious need these days, and not many solutions out there, especially if you can't afford expensive lab stuff.
One question would be: over how long a period of time do you need to average the current draw? Obviously, many options will fall short for long periods as they will accumulate error over time.
Amper:
Yes, all this micro power stuff is an entire rabbit hole on its own. The more you try the more problems you discover and the solutions are sometimes unconventional or just plain ridiculous.
For now i guess a full log of 5-10h would be nice since every period will take up to an hour (heavily depending on tube and capacitor choice). So 10h should give me roughly 10% accuracy if i miss one charge cycle. Though from there on it would be pretty simple to just add another layer of averaging. Since im only interested in the average its no problem to throw away all the measurements and just log a single value every hour or so. That should also give opportunity to log changes due to environmental changes like slow humidity or temperature change.
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