At last, we have a resistance for a '72 TR6 ammeter. (Thank you Brian !)
The specimen measures 2.7 milliohms, so 8" of 16 gauge copper would make
a 50% shunt.
YMMV
Randall
Randall Young wrote:
>
> Hello listers :
> I just measured the resistance of two Lucas ammeters (both from 59
> TR3A's, with the setscrew terminals), using fairly accurate digital
> meters. Both are 1.2 milliohms.
>
> Some quick work with a resistance table & calculator shows that a 50%
> shunt (equal resistance) could be made from 5.5" of 14 gauge copper wire
> (8.29 milliohms/meter) or 3.5" of 16 gauge copper (13.2
> milliohms/meter). At 30 amps (50% of 60 amps total), the shunt will
> dissipate 1.1 watts, which shouldn't be a problem.
>
> Just for grins, I measured a 60 amp "no name" ammeter at 32 milliohms,
> much higher than the Lucas.
>
> Of course, "your mileage may vary" <g>
>
> My apologies to the person who I suggested start with 4" of 14 gauge.
>
> If anyone is still interested, I can probably borrow & measure a TR6
> ammeter, but it might take a while.
>
> Bill : Know of anyone in the area who might loan me one ?
>
> Randall
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