wwhitney
Active Member
OK, I realized that I do have one handy, namely my little compact fan + toaster element (resistive heater) space heater, with a 2 prong plug and simple mechanical switches. When I turn the space heater to the medium setting, then I can measure across the 2 prongs of the plug to get the cold resistance of one of the two heater elements, in parallel with the windings on the motor.A more directly applicable test would have been to insert, say a 5 ohm resistor into the circuit, and see how the DMM is affected while measuring that resistance. But I didn't have one handy.
So motivated by an interest in science and goaded by qdeathstar's intransigence, I was able to take the following resistance measurements with my DMM.
14.8 ohms = Space heater configured as above
0.1 to 0.3 ohms = Unloaded N-G resistance at receptacle
14.9 to 15.2 ohms = Unloaded N-G in series with space heater
17 ohms = N-G in series with space heater, with hair dryer on fan only (low load)
41 ohms = N-G in series with space heater, with hair dryer on low (medium load)
0 ohms = N-G in series with space heater, with hair dryer on high (high load)
As you can see, the DMM result depends on the current that is flowing on the neutral conductor that is being measured. So if you try to take a measurement on a powered circuit, your result will be off.
So for hopefully the last time, as the manual tells you, only take resistance measurements on unpowered circuits.
Cheers, Wayne