You use an ohmmeter that can measure down to milliohms.
Preferably it has a null button.
You measure from a point on one metal end in the middle of the plate to a point immediately next to it. Like a mm away.
Move the other probe around for the lowest reading.
You either note this reading or better yet use the null function on the milliohmmeter to adjust to a reading of 0.000 ohms.
Without moving the center-of-the-plate probe you move the other probe to the center of the other plate. Move it around a bit until you get the lowest reading.
Note it. That's the resistance value you seek.
If no null function you subtract the original reading from this two ends reading.
Any probe has contact resistance that will skew the resistance reading give a non-true value of the in-service resistance. The above technique is to remove the contact resistance from the measurement.
Note that resistance measurements that are lower than 10 ohms are heavily by the contact resistance between the probes and the surfaces contacted. For critical measurements in that range, a four-terminal, Kelvin, measurement
is way more accurate and obviates the contact resistance by independently supplying the current through two connections and using the other two connections to measure the voltage drop. Then R = V/I; this method is preferred for accurate measurements in the milliohm range.
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!
Note that while zeroing the meter works, it requires moving the probe(s) to properly do the offset correction, and the contact resistance is not necessarily a consistent value, since it depends on the amount of force, penetration of oxides, surface contaminants, etc.
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!
Ask around the electronics lab for a 4-wire milliohm meter. 4-wire meter zeros out the probe wire and clamp contact resistances at each end. Oh, I see IRstuff already mentioned that method.
Acceptance tests on that type of gear is often done with an instrument called a "Ductor".
It puts a heavy current through the bus bar or connection under test and measures the voltage drop.
Test currents may be in the range of 10 Amps or more.
Bill
-------------------- Ohm's law
Not just a good idea; It's the LAW!
