> Can someone help me understand why around the time of cars switching from
> generators to alternators, cars that actually HAD gauges switched from
> ammeters to voltmeters? They seem to give very different information.
Why
> not both?
Just Ed will probably flame me again for daring to presume to know anything,
but my filters are up, so he will have to get up the guts to post to the
list for me to see it ;-)
John,
It is not a coincidence.
In short, the voltage tells you more about what is happening and the
ammeter's information is generally irrelevant in a normally-functional
automotive electrical system, although it can still be a useful tool when
things are not working properly.
DC generators tend to start charging around 2000rpm and your electrical
system therefore tends to be discharging at anything lower than that,
therefore the use of an ammeter to let you know whether you are currently
running off the generator or the battery.
Alternators can be charging at any rpm (idle or higher, of course) and the
important thing to know is the voltage your electrical system is currently
registering. An ammeter at this stage is less useful because the voltage
level already tells you that your alternator is charging and it can also
tell you if you are no longer regulating the charge (too high of a voltage)
which the ammeter cannot do.
David Lieb
1972 RWA Midget
2002 GTI for Trish to beat me at autocross with
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