[DeTomaso] Amp gauge

[Kirby Schrader]

Ah, well....

In the case of HP vs Torque.... there is no discussion!

I want BOTH!!!!!!!!

Lots of each!


On May 19, 2012, at 11:24 AM, Jeff Detrich wrote:

> In my experience, all the ammeter was supposed to do is measure whether the
> battery is in a charge, nuetral, or discharge state. Back in the old days
> when cars had amp gauges, that was pretty important since there wasn't much
> sophistication in the electrical components, ie, they were on or off or you
> had a short somewhere. As to the Voltmeter vs Amp gauge issue, it's sort of
> like HP vs Torque.
> 
> Jeff
> 6559
> 
> ___
> 
>> From Wikipedia Answers: (interesting point on the use of a shunt)
> 
> There are two main wires that normally come off the battery, one extremely
> large one that feeds the starter, and one reasonably thick wire (usually
> around 10 ga) that feeds everything else in the
> car<http://wiki.answers.com/Q/How_does_an_electric_ammeter_work#>
> .
> 
> A classic style ammeter runs in series with the battery wire that feeds
> everything else in the car. It samples which way the current is flowing and
> how much current is flowing. If the alternator is pushing current into the
> battery (charging the battery) the gauge reads positive. If current is
> flowing out of the battery, it should read negative, and usually means that
> your charging system is not keeping up with the electrical demands.
> 
> Since the classical ammeter is hooked up in series, it involves very thick
> wire (like 10 ga) to be routed all the way to the ammeter in the cockpit of
> your car. With all that current flowing through the ammeter, a short
> circuit on the ammeter in the cockpit can be fairly dramatic, and some
> classic car guys avoid ammeters for the possibiilty of causing a fire.
> There is also an ammeters out there that have an external shunt. An
> external shunt is basically a very low value resistor that is in series
> just as the ammeter was in the previous example, and then the ammeter is in
> parallel to the shunt. Basically MOST of the current goes through the shunt
> and only a small percentage goes through the ammeter. By knowing the
> resistance of the shunt and the meter, the meter is able to calculate the
> total current by measuring only the small current that goes through the
> meter. This kind of setup allows small wires to be run to the ammeter in
> the cockpit, and the high current to remain in the engine compartment. The
> danger in these setups on some old
> cars<http://wiki.answers.com/Q/How_does_an_electric_ammeter_work#>is
> there isn't a fuse on that small ammeter wire, So if the shunt is
> damaged or a connector breaks, it would try to flow all the current through
> the remaining path which is the small ammeter wire and that would melt that
> wire (along with whatever else it is next to).
> 
> Read more:
> http://wiki.answers.com/Q/How_does_an_electric_ammeter_work#ixzz1vKfrSMNK
> 
> On Sat, May 19, 2012 at 10:46 AM, Guido deTomaso <guido_detomaso at prodigy.net
>> wrote:
> 
>> 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.
>> 
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