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variable gain current amp

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Simon:

--- Quote from: Jay_Diddy_B on May 15, 2020, 02:12:04 pm ---Hi,

I think that double measuring and shorting shunts is the way to get really high dynamic range.

Dave did a review of device designed to this in EEVBlog 1304. Look at 31:00 mins plus. There are multiple shunts and a pair of shorting MOSFETs.

Quitech Otti USB power measurement and battery analyser: https://www.qoitech.com/

The question is how good do you need to be?

Regards,
Jay_Diddy_B




--- End quote ---

they seem to have used some opamps that look quite neet https://www.analog.com/media/en/technical-documentation/data-sheets/14901afd.pdf but actually have 100µV offset to the 3µV of the LTC6102

Jay_Diddy_B:
Hi,

You live with a large offset if you have a large signal. I think that there are three shunts in the Qoitech device:



One is 1 \$\Omega\$
Another is 22 \$\Omega\$
I suspect that the third one is a low value.

Regards,
Jay_Diddy_B

Vovk_Z:

--- Quote from: Simon on May 15, 2020, 05:33:19 pm ---it will go to a panel meter. I can get meters that measure 200mV, 2V, 20V. I don't need it to be highly accurate.

--- End quote ---
- but there are ready-made manufactured 5 Amps 5 digit ammeters?
Look here.

Simon:
You want me to trust something off ebay? I know I said I did not need it highly accurate but I did say it needs to be repeatable. What if those things drift?

Vovk_Z:
It is more repeatable than you can make at home.

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