This is now the third try at sending a message to the group. Here's
what I wrote before:
I sent this on the 18th, but it didn't show up, so here goes another
try. I don't know if something's wrong with my email. Please excuse
if the redundant original shows up too.
Original message:
Yes, it is common-mode noise, and maybe some leakage paths - if you
measure in-circuit, you are also seeing the effects of everything
else those parts are attached to, interacting with the different
impedances of the ohmmeter inputs. You'll get identical swapped
readings only on parts that are in perfectly symmetric circuits - not
often encountered. You may get some improvement by connecting the DMM
guard terminal only to the DUT chassis, and of course don't have the
DUT plugged in. The best accuracy should be with the "common" or
"low" DMM input tied to the cold side of the component - the end with
the most circuitry attached, or lowest impedance to the rest.
I'd recommend not worrying about it - if the values are within a
percent or so in one direction or the other, then close enough. Any
that aren't you can remove and test out of circuit to make sure. I
doubt that you'd even be able to notice the difference on an old
analog meter - the meter movement's retrace/repeatability probably
wouldn't be good enough to see it anyway, from one test to the next.
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