"Denny" writes:


Someone should make a panel display
with LED's for all three, and a small digital meter that will cycle
between them.
************************************************* ****************

Well, that would be a nice gadget, but I do take exception with the
need for an amp meter in flight

But it WILL tell you that both {*}ators are working; not just one.
Or than one is doing 90% of the work, and the other 10%, etc.

(You can force the issue, to be sure. On the ramp; load the system
-- all lamps, electric heat props, whatever. Run up #1 and see what
happens. Throttle back and repeat w/#2. You don't need matched
regulators to see that both sides charge -- but in flight, I'd rather
have..

alternator on it's last living diode at 12.0 volts, and you will not
show a big discharge on the amp meter, but you are in for deep doo doo,
very soon... Give me a good volt meter any day...

On a twin; I'd want two single-ended ammeters, one on each {*}ator.
Not the zero center kind that tells you NET gain/loss the battery.
Then a good voltmeter on the bus/battery.

As for bad diodes; I trust my ears. But ammeters will tell you.

Luckily, aircraft share the 12 volts with autos, and any auto store
will have an expanded scale DC voltmeter that you can plug into the
cigarette lighter... Have one of those in the plane and you can
quickly verify that the alternator is doing the job or not... None of

With this proviso... that kind of crap [engineering term of art] is
notoriously uncalibrated.
http://www.its.bldrdoc.gov/fs-1037/dir-001/_0125.htm But so what?
You just want REPEATABILITY. Borrow a DVM and calibrate it with your
car, if nothing else. Mark the face at oh say 14v, 12v and maybe 15.

Then gather experience as you fly.

Note, BTW, that even a cheapo DVM typically offers good accuracy;
all the magic is the chipset and oscillator. Buy one.

this waiting for the amp meter to go into discharge to tell you are in
trouble - which is way too late - the volt meter will warn you of
impending problems long before the battery goes toes up...

Maybe....BUT one side could be all but dead and the other
coping just fine...until...



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