"Winston" wrote in message
...
On Wed, 08 Aug 2012 11:44:59 -0700, PrecisionmachinisT wrote:

"Winston" wrote in message
...
On Wed, 08 Aug 2012 12:37:40 -0400, Jim Wilkins wrote:

(...)

If you want to measure winding resistance accurately, force about
an
Amp through it and measure the voltage drop. At 1A, 1 mV is one
milliOhm.

Yes. A Kelvin connection. It is very useful.
http://en.wikipedia.org/wiki/Four-terminal_sensing

My old Triplet 630 seems to work just fine for this and since the
"B"
cell only needs replacement about once every 30 years......

That's peachy for getting a 'ballpark' idea and probably quite
sufficient
for most motor servicing without the need of a Kelvin connection.

When you *do* need much better precision and accuracy, a Kelvin
connection with a good digital meter is hard to beat. In a previous
lifetime, I was able to estimate current flow in a very low
impedance
application by using a measured PCB trace as my current shunt.
'Worked a
treat.

--Winston

I have a nice calibrated lab milliOhm sitting in front of me. I doubt
a Triplett can show it's actually 0.6 microOhms over.

jsw