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alternator ripple

Printed From: the12volt.com
Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=108600
Printed Date: May 13, 2025 at 10:05 PM


Topic: alternator ripple

Posted By: reax222
Subject: alternator ripple
Date Posted: November 01, 2008 at 6:32 PM

I have a fluke 117 which does frequency and I was curious if it would be able to detect alt ripple. If the battery is in good condition, I wouldn't expect it to, but if the battery was weak or failing, then would it pick up ripple as a frequency?

Because it's three phase and the mostly cut off, there wouldn't be much amplitude to the ripple. Because of the three phase, I would expect the frequency to be 1/3 of the engines rpm or pretty close. It would be a decent test for a bad diode or a poorly filtering battery?



Replies:

Posted By: i am an idiot
Date Posted: November 01, 2008 at 6:45 PM

I really doubt there will be enough amplitude for the meter to pick up.  If it were able to pick it up, Just looking at the size of the pulleys, I would think the alternator would turn at least twice as fast as the crankshaft.  

You would probably have better luck reading AC voltage at the alternator.  I am not familiar with the 117 but if it has an AC  Millivolt setting you should be able to get a reading there.


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