160403-1440 EDT
zach_zachary1:
Something is fishy. Any ordinary device called an ohmmeter would be destroyed with 120 V 60 Hz or DC applied to its terminals. Can I design a device to mreasure DC resistance and not be destroyed by qpplying 120 V to the terminals? Possibly, but I have not applied any thought on how to accomplish that.
What is the DC resistance from an outlet back thru the secondary of the power company transformer measured with the primary unenergized? Quite low, probably mostly in the branch circuit wire. To this you have in parallel all of the shunt load from other circuits, yours and your neighbors. These are not low resistances, but they contribute to reducing the resistance that would be read. My guess is that the secondary DC resistance of a small residential transformer is less than 0.05 ohms. Current at 120 V and 0.05 ohms is 2400 A. #4 copper wire is 0.25 ohms per 1000 ft and #12 is 1.6 ohms per 1000 ft. A breaker resistance is fairly small.
Read your Fluke manual and see if there is any designed in protection. I don't believe there is any way the meter is reading the DC circuit resistance. Often times with Fluke probes it is difficult to measure fractional ohms. The meter itself will read 0.0 ohms with a short between two banana plugs. With good probes shorted together the lowest I get is 0.1 ohm on my Fluke 27. With not so good probes I get 3 ohms.
We really need to know how your Fluke meter works in its ohms position.
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