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Recently I have been doing some measurements with a multimeter on some new transformers for my company. Lately I have noticed the resistance of the multimeter in current mode (ammeter) has increased. Other multimeters measured less than 1 Ohm across the mA measurement points in mA Mode while the multimeters I am using are now showing 2,4 and 14 Ohm. The A Mode points still have low resistances. I have searched everywhere and not found a thing. I have been measuring mains for some of the tests.

Does anyone have an idea why this would be happening? I have checked fuses and they are fine.

Thanks, et.

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    \$\begingroup\$ What were the original measurements? \$\endgroup\$ – analogsystemsrf Oct 30 '18 at 14:10
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    \$\begingroup\$ There is no required resistance for amps measurements, its perfectly fine for one model to have a different burden voltage than the other. \$\endgroup\$ – PlasmaHH Oct 30 '18 at 14:14
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    \$\begingroup\$ What does the meter's manual say the burden resistance should be? \$\endgroup\$ – Elliot Alderson Oct 30 '18 at 14:17
  • \$\begingroup\$ Not clear on the issue- Are you saying that the exact same meter has a shunt resistance that is increasing, or are you saying that different meters have higher resistance than other meters that you have been using? \$\endgroup\$ – John D Oct 30 '18 at 14:48
  • \$\begingroup\$ I am unable to measure another one of the 14 Ohm (it's an Amprobe 37XR-A). I can't find any manual on the Amprobe 37. The Amprobe 38 manual says it should have a burden of 1 mV/mA i.e. 1 Ohm. The 2,4 Ohm one is a Fluke 17B+. Another Fluke 17B measures at 1,9 Ohm so it seems about right, but maybe a bit high. I did not consider it could be that high. I can't find any burden information on the Fluke devices. \$\endgroup\$ – etienz Oct 31 '18 at 6:19

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