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Old 06-24-2010, 01:32 PM   #11
rotorwrench
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Join Date: Jun 2010
Location: San Antonio, Texas
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Default Re: Ammeter vs Voltmeter

Some aircraft still run an amp meter but they have to either run a shunt or a shunt wire to control resitance on one side of the meter. With a 70 amp system you have to turn on all the lights, landing light, etc. just to ge the meter to move a tiny fraction but it will show a discharge of about a needle width when it ain't chargin.

We also put in an accessory volt meter to make sure the battery voltage is high enough to start the engine. We mostly use 24-volt batteries but still have some 12-volters. We set the regulators to give near 14-volts on a 12-volt system and 28-volts on a 24-volt system. If the volt meter doesn't read 14 or 28 volts or at least battery voltage, the charging system isn't working. If your charging system isn't working, voltage will steadily drop till it won't run anymore. That's another reason aircraft still use magnetos. You can still run if all else quits.
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