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Measuring 100A DC current

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HighVoltage:
We discussed this before:
https://www.eevblog.com/forum/metrology/calibrating-a-100a-dc-shunt/

Not in your price range but this is what I have used very successfully for 100A DC:
The RUG-Z-R001-0.1-TK1

https://www.distrelec.de/de/leistungswiderstand-1mohm-250w-isabellenhuette-rug-r001-tk1/p/16057580?queryFromSuggest=true&itemList=suggested_search



coppice:

--- Quote from: nctnico on June 08, 2024, 09:27:57 am ---The self inductance will be too high when using wirewound resistors.

--- End quote ---
Too high for what? Has there been any indication of how much inductance the OP's application can tolerate?

johansen:

--- Quote from: nctnico on June 08, 2024, 09:27:57 am ---
--- Quote from: AVGresponding on June 08, 2024, 07:57:55 am ---If "cheap" is the primary operand, I'd buy a couple of hundred of something like these and bin them to get a hundred with the correct values to make a 500W 10mΩ 1% shunt. Also you'd have a hundred spare resistors for your stock afterwards.

--- End quote ---
The self inductance will be too high when using wirewound resistors. Especially if the current is switched off quickly you can get quite high voltage swings. This is already a problem with low inductance, planar resistors at 15A.

Another advantage of using a current shunt over a hall-based current probe is having a high pulse handling ability. So you can measure short pulses to hundreds of amps without needing a current probe which is rated for hundreds of amps (which may also have a higher offset / noise floor).

--- End quote ---

You seem weirdly confident that 100 resistors in parallel will have too much inductance.

Does a 3 inch long shunt have too much inductance for you?

BillyO:

--- Quote from: johansen on June 08, 2024, 07:16:00 pm ---You seem weirdly confident that 100 resistors in parallel will have too much inductance.

--- End quote ---

100 of those resistors in parallel would not have very much inductance, depending on the frequencies being applied.

However, the final device would be kind of large and unwieldy.  The resistors are about 1cm square and if you put 1cm between each for cooling then put them in a 10 x 10 matrix it would be square 19cm on a side!

johansen:

--- Quote from: BillyO on June 08, 2024, 07:34:37 pm ---
--- Quote from: johansen on June 08, 2024, 07:16:00 pm ---You seem weirdly confident that 100 resistors in parallel will have too much inductance.

--- End quote ---
100 of those resistors in parallel would not have very much inductance, depending on the frequencies being applied.

However, the final device would be kind of large and unwieldy.  The resistors are about 1cm square and if you put 1cm between each for cooling then put them in a 10 x 10 matrix it would be square 19cm on a side!

--- End quote ---

didn't look at them till now. yeah would not use those.

6$ on amazon - 100 1/2 watt resistors.
https://www.amazon.com/EDGELEC-Resistor-Tolerance-Multiple-Resistance/dp/B07XLBY5RF

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