[TR] Ammeter shunt

[Randall]

There are different approaches; mine is quite a bit different than Dan's.

What I did (the first time) was to undo the ammeter mounting and let it
(carefully) hang out of the dash while I experimented with adding strands of
steel wire across the ammeter terminals.  I first noted the needle
deflection with the headlights on; and then added strands of steel "handy"
wire until the deflection was about half of it's original amount.  As I
recall, the wire was about 18 or 20 AWG, just ordinary steel "handy" wire
(aka baling wire) and I wound up with 3 or 4 strands of it, just long enough
to reach across the ammeter terminals.  Once I was happy with the division
ratio, I reinstalled the ammeter in the dash, with the wires still in place.
That setup worked fine for many years, with my 60 amp Ford alternator.

More recently I got fancy, and measured the resistance of several TR3
ammeters.  From that measurement, I calculated the length of insulated
copper that would produce the same resistance, and added that across the
terminals.  Here's a photo taken as I was disassembling the car after it got
wrecked:
http://fwd4.me/0gSZ

According to my notes, I measured the resistance at 1.6 milliohms (or 0.016
ohms, obviously not with an ordinary ohmmeter), and used 3.5 inches of 16
AWG copper wire.

But of course before applying either approach, you'll have to straighten out
your wiring so the ammeter reads current to/from the battery.  It may have
changed later, but the instructions I got from Dan show this as the "60 amp
ammeter option" in figure 9.

-- Randall