I have a 70W 12V-500V DC power converter, and something in these pictures is not adding up.
I run the 500V output through a high-voltage 332kΩ resistor.
Now, using the left multimeter I monitor the current through the circuit, and it runs up around 320mA. Using the right multimeter I first check the voltage on the power supply leads: 511V. (So right away we know something's off -- the supply isn't even getting warm after a few minutes of testing.)
I verified the resistor's value with both meters. If all of this is true then Ohm's law suggests that either the voltage across the resistor should be .320mA * 332kΩ = 106kV, or else the current through the circuit should be 511V / 332kΩ = 1.5mA.
(Of course the right multimeter itself is providing a path for current, but its resistance should be very high. Indeed: when I remove the right multimeter from the circuit the current increases only 2-3mA.)
My best guess is that the output of the converter is not very smooth DC, or has some characteristic that is causing these multimeters to produce erroneous values. If so, what characteristic might that be, and how can I adjust for it?
And in case the wiring isn't clear from the photos, here's how it was connected
And here's some more information. First, to remove all doubt, here's the resistor being measured after all this, so it does not appear to have fried.
And here is the whole shebang. If the ammeter on the DC supply can be trusted, and this power converter doesn't have the ability to produce power out of thin air, then the true circuit current is under 3.6mA. (This is consistent with the fact that I have observed no heat buildup on any component whatsoever.) In which case the question is: Why is the Extech reading ~320mA? If I switch the Extech to µA scale it reads around 3180 (still not right). The other multimeter reads 0A at all scales, which is consistent with the voltage drop seen across the resistor (which implies 36µA true current).
Epilogue: I opened the Extech multimeter to find its 250mA fuse blown. Replacing that made it behave normally. Evidently it just has a very confusing failure mode!