[DeTomaso] Amp gauge

Guido deTomaso guido_detomaso at prodigy.net
Sat May 19 11:46:01 EDT 2012



I'm with Tomas, Mike, Forrest on this.

We call an "amp gauge" on a single wire in and out of the battery an "ammeter", 
but the same gauge on the single wire out of the alternator a "loadmeter".  It 
sounds like Kirby's GT40 "ammeter" was wired as a "loadmeter".  Gary's comments 
below seem aimed at a loadmeter ... but there's no one voltage that's a line 
between discharging and charging, and unless you've got some electronics that 
need at least some minimum voltage, I don't see any "critical info" coming from 
a voltmeter.  IIRC small aircraft only have ammeters.

Far below, I didn't understand John Taphorn's comment at first.  But upon 
re-reading he's speaking to putting a "shunt" around the ammeter, so 
less current goes through it.  But John Buckman's idea was a remote shunt with a 
matching gauge, there's no reason to expect that not to work properly.  I've got 
such a set-up, Stewart Warner brand, in the "project bank", as always don't hold 
your breath on that.

GD


I completely agree with you Kirby. I see an amp gauge perhaps useful in
the design of a car but once a car and electrical system is designed to
carry a specific load, reading the load is a bit unnecessary unless there
is a problem. Problems can come in many sorts.

An amp meter is useful in that it can give you some idea of load in a
problematic situation but it isn't going to give your critical info. Is
your alternator charging, before you start up what is your voltage, etc.
When you know where your voltage is in charging you know anytime the
voltage comes off that mark you have an issue and often load has nothing
to do with it. A short would; in that case you just look for the smoke.

I can see the wow factor in an amp gauge but with a properly designed car
it just doesn't give you the critical info a volt gauge does. Great, your
headlights are on and your fans are on and you can see what the load is.
If your alternator cannot keep up the car was improperly set up
electrically.

Gary

Yes, you can use a shunt; however, your gauge will no longer be 
accurately reading the quantity of charge/discharge without 
recalibration.  It is about as useful as an idiot light at that point.  
Idiot light on, you are discharging, idiot light off you are charging.  
I haven't heard of anyone using a shunt recalibrating their amp gauge.

JT


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