When testing large MVA power transformers, like 66kV to 16kV, the winding resistance in DC ohms is milliohms.
It takes a high current supply to do this, then the V is measured across the winding to determine the resistance using Ohm's Law. If the resistance is less than 1 ohm, why does a 9V digital multimeter show infinite ohms?
I am guessing/assuming that there is a physics explanation. My guess is that the electric field created in the conductor (winding) from a 9V battery is not enough to polarize the mass of electrons in the primary winding.
It also intrigues/confuses me that I can use a 9V DMM to measure other primary windings on smaller transformers with no problems. How long is the coil of wire in a primary winding (approximately)?
So why does a 9V DMM yield infinity when the real primary winding resistance is in milliohms?