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4-wire Bench DMM questions

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zargnut:
I just ordered a rigol 3058 after a good experience with their little oscilloscope. I got it primarily because space and depth of shelving is very limited, and can't accomodate a used HP/Fluke. Does anyone have any experience with the DMM? Dave, think Rigol will give you a DMM to eval?  ;D Maybe they forgot about the mods...

regarding fabricating a set of 4 wire leads. I have a bunch of beldon 1192 quad mic cable laying around and was wondering if I could use this to wire up a 4-wire set that terminates at two micro-clips.

wire specs:

http://www.belden.com/techdatas/english/1192A.pdf

thanks for any advice.
dan

alm:
I don't think cables for 4W resistance measurements are very critical, the whole point of 4W measurements is to eliminate lead/contact resistance. Be sure to use proper clips, with the only connection between the two wires through the wire you clipped on, regular crocodile clips will short the two wires, so contact resistance between the jaws and the wire (the largest variable) is still an issue. You can actually do good resistance measurements with just for wires with four clips, you just need a larger area to clip on to, and it's more hassle.

You could connect the shield to the guard terminal if your meter has one, see the manual for proper connections in that case. Note that you'll probably only use two of the four conductors, since you typically want two separate cables. I would connect two in parallel, since the commercial leads tends to have a larger wire gauge than 24 awg.

mikeselectricstuff:
Clips for 4-terminal measurements are called kelvin clips :
http://uk.farnell.com/silvertronic/502001/insulated-kelvin-clip/dp/1851741

zargnut:
awsome, thanks.

regarding the wire gauge.. with the low impedance wire and short length, does the gauge really matter for 4wire resistance measurements?

Do the sensor and current leads share a ground? IE could I wire the copper sheath to both grounds and double up the insulated conductors for each + sense/current wires? Or am I missing the whole isolated circuit point here?

mikeselectricstuff:
with 4-wire measurement, resistance of the leads is cancelled out, so pretty much any wire will work. The 4 meter terminals are connected with 4 seperate wires to the clips.

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