Products > Test Equipment
Measuring 100A DC current
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gaminn:
Hi,
occasionally I need to measure current up to 100A DC, which is obviously too much for any handheld multimeter. I found e.g. this shunt https://www.aliexpress.com/item/1005005721758936.html. It promises +- 0.1% accuracy. I would use digital multimeter to read voltage drop accross the shunt (75 mV @ 100A) and then calculate the current. It would be nice if the shunt was 100 mV, then no calculation would be needed....

Is there something better for max 100 USD that can measure 100A +- 200 mA?
Martin72:
Hi,

It should not be more than 100mV.
At 100A, this is already 10W, which heats up well and influences the measurement result, which has a corresponding effect on the accuracy.
Here is a shunt that has 0.25% tolerance and 1mV/A:
https://de.rs-online.com/web/p/shunts/8233589
BeBuLamar:
For such a high current I would use a clamp meter which should have sufficient accuracy and much easier to use.
Martin72:
But that is precisely the problem.
Finding a current clamp that is that accurate.
If you're lucky, you'll find one with 1%, which is already very accurate for a current clamp, but costs much more than a current shunt, which is even more accurate.
Stray Electron:
    Even the best clamp on DC amp meters (Fluke, AEMC, etc) are only rated for 3% accuracy.  Forget the cheap made Chinese meters.  Clamp on amp meters are pretty trivial but DC current meters are very tricky and expensive.

   I would use a good quality American made current shunt and meter and keep your measurement time short in order to avoid heating up the shunt.  American made current shunts are almost always designed to output 50 mA at the fully rated current so a 100 Amp shunt will need to dissipate 5 Watts of power (0.050 x 100) so power dissipation and heating of the shunt shouldn't be hard to deal with. 

   Good quality current shunts and the corresponding 50mA meters can be found cheaply on Ebay. Here is just one example, this is a 400 Amp shunt that outputs 50mA.  https://www.ebay.com/itm/404932876476?itmmeta=01HZQWBXFRHYMQP7DY3KJFZ527&hash=item5e47e158bc%3Ag%3AW70AAOSwB1JkLYUd&itmprp=enc%3AAQAJAAAAwIFn1Fck%2FY3gpneHseC0olXbRZuhefV3YEwPVSqu3eK714H%2BIDsGa%2FtWRJD67lBpuoJDAtWuYwJb1eMsIigKuPFBza5ZcxyyOUx3UR7Zk3L2KoTiieJOX%2FkXvAVv%2FBVoYe0hDPwBDjJdqj7J2p6ymW13DGTtMekzmSiJNCmJ9udmJKTsGW3ZRlp5%2FxcKsQbZTx9kTueS0W2QDtJUg5Oo9giGoiyZoFe9ZwkKEreNHj%2Fc2GJfjfSsFO37aUyUv3hUYw%3D%3D%7Ctkp%3ABk9SR4TYr_z9Yw&LH_ItemCondition=4
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