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post #1 of (permalink) Old 10-13-2003, 01:41 PM
woodcarver
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Ammeter vs. Voltmeter

I have looked at the archives for this and have had no luck.. I understand the difference between a voltmeter and an ammeter (guages) but not sure which would be better to put in my '94 Tracker. What is your preference? I am gonna put a triple guage set (temp., oil press, volt or amp) in and would like to know what her "vitals" are (factory guages don't give enough info until it is too late).
Thanks in advance,
Mac

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post #2 of (permalink) Old 10-13-2003, 01:46 PM
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Re: Ammeter vs. Voltmeter

Don't use an ammeter , you have to route the entire vehicle's electrical load through it to make it read properly . A voltmeter will let you know running volts , actually more useful than you think . If the sytem drops below 13.8 running , something is either using too much or the alt is weak , ect....
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post #3 of (permalink) Old 10-13-2003, 04:23 PM
 
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Re: Ammeter vs. Voltmeter

Ampmeters work better on the old type charging systems that use a generator. Since the voltage on these old systems vary depending on engine speed they use amps as the systen of mesurement of the generators charging output.
With the advent of the alternator which provides a constant voltage no matter the engine speed the unit of measurement switched to volts. Any signafent voltage drop indicates either a bad charging system or you are using more voltage than the system can produce.
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post #4 of (permalink) Old 10-13-2003, 06:48 PM
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Re: Ammeter vs. Voltmeter

Not to be argumentative - it's mostly a matter of preference - and shoe leather.

The purpose of either a voltmeter or ammeter is to monitor the electrical system's performance and give early warning of failure - as early a warning as possible.

IF - and that's a big word - IF the ammeter is properly wired like automotive systems have been since the 20's:
The ammeter is placed between the battery and everything else. The alternator or generator first feeds the entire electrical load (does not go through the ammeter,) then whatever's left over goes through the ammeter to the battery. So the ammeter only reads, and passes, the current going to the battery to recharge it - a (+) reading. The only time the entire load goes through the ammeter is if the battery is having to provide the energy to the load -- a (-) reading like the alternator quit.

Whenever you get a (-) reading you need to know it - that's the early warning that you'll be walking soon.
The ammeter movement is far greater than a voltmeter's is and is noticable much sooner.
If the alternator quits charging and you are watching a voltmeter the meter deflection between 13.6 and 13.4 is slight. By the time the battery has discharged enough for you to notice it, it's getting so low you are probably getting ready to start walking.

Notice most all automotive ammeters only show +/- 30 amps, if the entire load went through it, it would need to go higher.
And - yes, ammeter is not misspelled - it's either ammeter or amp meter - 2 words.

Alternator, generator, or nuclear reactor - recharging the the battery is still the same.
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post #5 of (permalink) Old 10-13-2003, 07:46 PM
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Re: Ammeter vs. Voltmeter

Correct on the ammeter. It shows the relationship between the electrical load and the battery, that's it. If you have 5 bizillion gizagawatt alternator, it will still only show how much (if any) power is being DRAWN from the battery or CHARGING the battery.

If the battery shows a + all the time, your battery is always charging (bad battery or bad voltage regulator). If the gauge shows - all the time, you're draning your battery.

I'd prefer both. A GOOOOOD ammeter is a MUST, high power is going through there and it's got to be SAFE and reliable.
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post #6 of (permalink) Old 10-13-2003, 09:53 PM
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Re: Ammeter vs. Voltmeter

Two reasons to put in a voltmeter. Just like Sarge said, you don't have to run the whole load through the meter, hence, you can use reasonably sized wire. Second, you get to see the condition of the battery with the engine off, and you get a good idea of the alternator output when the engine is running.
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