> If you don't have a low ohm meter, the next best way to measure its
> resistance would be to run a controlled amount of current through it
> and measure the resulting voltage drop. Most recent digital
> voltmeters can measure DC down in the millivolts and should do just
> fine. Some alloys can change resistance dramatically depending on
> temperature, so measure accordingly.
>
> 73, Bill W7TI
Hi Bill,
The best way to measure resistance is through the method you
outline anyway.
When roughing in low value resistances, connect the voltage
source across the entire length of the material and measure or
monitor current THROUGH the system. Use sharp probes to find
two points the right distance apart that produces the correct
voltage drop (on a high impedance meter) for the current flowing
through the resistance material.
Then when you make good low resistance connections to that
point, you'll have the resistance you want.
If you don't use this method, you have to repeatedly make nearly
perfect connections while seeking the correct resistance.
BTW, home made low resistance shunt should always be made
this way. Apply the source across a slightly LONGER length of
material than needed, and tap the low-current meter across a
slightly smaller portion of the shunt element. The same goes for
circuitboard mounted shunt resistors, tap the meter right at the
terminals of the shunt on it's OWN traces.
73, Tom W8JI
w8ji@contesting.com
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