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From: "george edmonds via groups.io" <G6HIG@...>
To: [email protected]
Sent: Monday, October 12, 2020 2:13:48 PM
Subject: Re: [HP-Agilent-Keysight-equipment] HP-3456A - Question Regarding Resistance Measurement

Hi Barry

Contamination will make resistors go down in value not up. How old are these
resistors, are they NOS. Resistors invariably go up in value with time,
especially if over 10M.

73 George G6HIG Dover UK On Monday, 12 October 2020, 20:06:34 BST, n4buq
<n4buq@...> wrote:

Not in a strict sense.? Both were at relatively the same ambient temperature
(they'd been in the same environment before testing).? I mostly held them
by their leads but did notice that I could change the resistance slightly
by touching them which I sort-of expected given the high resistance of
either one.

This wasn't exactly a laboratory-controlled experiment and there could have
been some temperature differences between the two but I'd suspect it wasn't
that great.

I wonder if I need to clean them a bit better before testing them again.? I
presume hand oils might affect these with the 90M seeing more of that than
the other.

Thanks,
Barry - N4BUQ

----- Original Message -----

From: "Bruce" <bruce@...>
To: [email protected]
Sent: Monday, October 12, 2020 1:58:59 PM
Subject: Re: [HP-Agilent-Keysight-equipment] HP-3456A - Question Regarding
Resistance Measurement

Did you considet temperature coefficient
Quoting n4buq <n4buq@...>:

I have two brand new 1% tolerance, metal-film resistors that I am
looking to use in a project.? One is 90M and the other is 50M and
I'm using my HP-3456A to measure them.

The 50M tests within 1% (around 49.8M).

The 90M tests at just over 92M which is about 2% over nominal.

2-Wire and 4-Wire show about the same differences.

My meter is not recently calibrated so I know I cannot really trust
either measurement; however, does it make sense that if both
resistors are indeed within 1% (as they should be given that they're
new), would one test correctly and one test incorrectly?

I realize that new parts may not be in spec and at least one of
these may be an example of that but these were bought from reputable
suppliers (e.g. not eBay purchases) so I suspect they are within
tolerance and my meter may be giving me false readings.

If both tested with the same relative difference (e.g. both showed
+2%), then that might make better sense but I'm curious as to
whether it's possible/probable that if both are in tolerance that
the meter would show that kind of variance.

Yeah, I know.? Weird question and maybe too many variables but
thought I'd see what the experts say.

Thanks,
Barry - N4BUQ