[volt-nuts] Best way to measure micro Ohms

[Chuck Harris]

If this stuff is what I think it is, it does contain
a sand of sharp, probably aluminum oxide, abrasive.

The idea is when you bolt the connection together, the
abrasive will break through the aluminum oxide layer
on the conductors, and will mushroom out the aluminum as
the abrasive burrows in, making lots of pure aluminum
metal contacts.

Usually, it also contains a dense oil to keep oxygen
away, and prevent further oxidization of the aluminum.

-Chuck Harris

george wrote:
> The reason that DC is used commercially to measure resistance is simple, if you
> use AC you may well get the reactive component as well as the resistance coming
> into play.
> 
> Such low resistance measurements commercially are normally only made on high
> current power distribution networks as part of a periodic test regime where you
> need to determine the quality/resistance of such things as bus bar
> joints/connections and loop resistance.
> 
> It is not a good idea to use copperslip around aluminium, there is an aluminium
> based version that should be used, but, be warned, just like copperslip it is an
> insulator, try putting your meter probes, set for resistance, into a tub of both,
> I have.  I do not know just why but the aluminium version is just like sand, it
> gets everywhere when you use it.
> 
> To check your joint I would use a four wire Kelvin set up using say 10 Amps from
> my constant current bench supply and then use my Keithly 616 digital  electrometer
> to measure the voltage/s present across the joint, a simple application of Ohms
> law will then give the resistance.
> 
> 73 George G6HIG _______________________________________________ volt-nuts mailing
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