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10A 0.1V CC source for handheld DIY microohm-meter

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Hi evereyone,

from time to time I need to measure DC resistances in the region of 1-500µOhm. At the moment I use a high resolution DMM (BM869s) and a lab power supply set to 5A in the usual 4-lead setup. It works quite well, I can measure down to about 1µOhm with an extra digit of resulution. Comparison with theoretical values showes me that my measurement errors are well below +-10%

Now I want to build a dedicated handheld setup with the flexibility to measure also at 1A and 10A. Power source could be batteries, a 12V wall plug or prefferably a USB power bank. I have build several projects with ADCs and shunt resistors. So I am not worried about measurement of current flowing and voltage drop. But at I am stuck trying to find a suitable current source. I looked for DC-DC converters but the high current ones only only work from 1.2V upwards in CC. Also, I do not need any voltages higher than 0.1V. In fact I prefer if the source is unable to supply anything above 0.1V. Looking at the power consumption, I do not think a CV-source with a power resistor in series is a good idea.
Ideally, I would look for a DC-DC converter with a spec of adjustable CC 0-10A and the ability to fix the voltage limit at below 1V.

Does anybody have a suggestion what search terms might help? Other ideas how to implement 1A, 5A, 10A CC capability without a full scale lab supply?

That should not be too complicated to build.
As a power source, I would propose a capable LiPo or LiIon battery.
Then you only need a shunt, an OPAMP with RR input, a small DCDC converter to generate the supply for it and a suitable MOSFET.
Additionally some protection or timeout circuit as you are dissipating up to 36W.

Page 20 of the LT3080 datasheet shows a circuit that can be modified for 10A.
It's probably not cheap though. If you want cheapness, then transistors and opamps are the best bet.

10 regulators in parallel? 🤔

Perhaps it’s best to use a CV DCDC intended for processors or DDR (low voltage, high current) to get you in the ballpark then use a linear ref to do the CC? It’ll be easier to get good noise performance and is simpler to design.


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