need 2-ohm 5w wirewound pot

[Alex [Temple-Heath List]]

Hi Ed,

The original design calls for a 2-ohm ww potentiometer in parallel 
with a 4-ohm resistor. This would be one of the four legs of a 
resistive bridge used to measure bellow one-ohm resistances. It has 
full scale ranges of 0.1, 0.5 and 1.0 ohms. The 2-ohm potentiometer 
is actually used to null out any resistance of the test probes. The 
article came out on the 1975 Electronic Experimenter's Handbook 
published by Popular Electronics. It's called "Build a Expanded Scale 
Milliohm meter.

If I end up having to use it, I think the 5-ohm unit that Digikey 
stocks might also work fine with some tweaking of the parallel resistor.

BTW, tried to reply to your email but it keeps bouncing back my 
messages. So apologies to the rest of the members for this on-list reply.

Thanks again.

-Alex

At 05:37 PM 3/19/2007, you wrote:
Yes, significant difference....

Do you need a variable resistance (2 terminals) or a voltage divider (3
terminals)

You could always put a 5 ohm resistor across it.

BUT.....  you have to be very careful with the rating and the maximum
current you pass through it.....

The Digi-Key unit has a max current of an ampere.....  even if you are
using it for a 2 ohm resistor....  then it's 2 ohms at TWO watts.....
not 5.  Mistake many people make the first time they use a variable or
adjustable resistor.....  all resistance values do not meet max power
rating of the whole device....

Ed

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