> What I don't understand, though, is its utility as a stand-alone item. Yo=
u could "do what it says on
> the tin" by just completely isolating the sense terminals from the force =
terminals and shorting the
> sense terminals together and the force terminals together. The only diffe=
rence I can see is that
> there would not be conductivity between the force terminals and sense ter=
minals and so therefore
> there could be a voltage difference between the two pairs.

I can see the utility of a device like this in calibrating temperature brid=
ges that use four terminal measurements on low resistance PRT devices that =
are used for measuring very low temperatures. We currently use Rhodium Iron=
 PRTs which have a room temperature resistance of around 36 ohms, and are t=
aking them down to liquid nitrogen temperatures. The measuring bridge has a=
 requirement that the cable between the bridge and the sensor has no more t=
han 10 ohms per wire, which starts adding up when using 30AWG wire to limit=
 the heat conduction down to the sensor from the outside world.

So yes, I can see it being a useful device in the calibration of very low t=
emperature measurement.



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