# Electrical question - influence of cold weather on resistance values?

Duncan Wood quatrro at dmx512.co.uk
Tue Dec 10 12:21:12 EST 2002

```Most meters read .2~.4 Ohms contact resistance on the leads, expensive
meters have a null button, very expensive solutions use 4 wires. Just
subtract the .6 Ohms & that tells you that the primary  side is connected.
What makes you suspect the coil?

From: "Duncan Thomson" <duncan at systemcontrols.co.nz>
To: <quattro at audifans.com>, <radek at istar.ca>
Subject: Re: Electrical question - influence of cold weather on resistance
values?
Date: Tue, 10 Dec 2002 12:14:07 +1300

Sounds like there is a problem with the meter, or at least the probes.
It should be zero when the probes are touched together, if the probes
have acquireda  resistance of 0.6 ohms then, yes, subtract that to get a
0.7ohm reading. The other possibility (pretty unlikely though) is that
there is a problem with the meter, and then who knows what the
resistance is...

You could check by shorting between the two terminals with a piece of
wire, to see if you get a zero reading... if so then get new leads, if
not, look for a new meter...

-10, ouch, that is cold...!
Cold temps will normally reduce resistance rather than increase it, but
not by very much...

HTH
Duncan
http://www.p-caronline.com/directory/udders
http://www.audifans.com/registry/view.php?action=viewMember&userid=359

> Please forgive my ignorance, I guess I must have skipped too many
physics classes in high
> school.
> I'm trying to diagnose a coil.  I measured primary resistance and it
came out at 1.3 Ohm,
> correct values,
> according to Bentley, are between 0.4 and 0.7 Ohm.  It was about -10
Celsius outside, real
> cold.
> Could the low temperature influence the reading?
> Another thing that makes me suspicious is that when I touch the two
ends of the probe
> together,
> I get a resistance of 0.6 Ohm.  Shouldn't it be zero?  My cheap
electrical meter does not
> have any
> adjustment knobs, should I just take the difference between the two