On Thu, 29 Oct 2020 21:55:51 -0400, Runner
wrote:

I have a spool of Teflon coated copper wire. I am trying to determine
the resistance of a one foot piece, but both of my meters read
differently. How can I get a reliable reading? I am using DVMs.
Thanks in advance.

If solid wire, measure the diameter of the copper wire. If stranded,
count the number of strands and measure the diameter of each strand of
wire. Also, measure the length of the wire. Hopefully, you have
more than one foot of wire. Then, go to a wire table, such as:
https://www.powerstream.com/Wire_Size.htm
Determine the resistance per 1000ft or per km from the table. The
math is:
resistance/ft * number_of_ft_length
and you have the resistance. That should give you an answer without
the ohms-guesser.

The problem you're having is typical of trying to measure fairly low
resistances with commodity hardware (i.e. a multimeter). To do it
accurately, you'll either need a milliohm meter:
https://www.google.com/search?q=milliohmmeter&tbm=isch
a Kelvin bridge:
https://www.google.com/search?q=kelvin+bridge+ohmmeter&tbm=isch
or possibly an ESR meter:
https://www.google.com/search?q=esr+meter&tbm=isch
The ESR meter might be a problem because it uses AC at 100KHz, which
is not exactly the same as the DC resistance. The cheaper devices
will also not work above about 10 ohms. For short lengths of wire,
the contact and lead resistance to the probes become a major source of
error, which will require a Kelvin bridge to eliminate.

If all else fails, PTFE insulated wire usually has the manufacturers
name and product number marked somewhere. Find these, search for the
specs, and you should get a number for ohms/ft or ohms/meter.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558