Alternator Noise

John@no_where.com (John_F) writes:

>Find or purchase a clamp on amp meter that will read both AC and DC
>amps. Turn on enough loads so that the alternator is generating at
>least 50% of it's rated load. Measure the DC amps and the AC amps of
>the alternator output. The AC current should not exceed 15% of the DC
>amps. If it exceeds 15% then you have a bad diode or stator winding.
>In many cases you can not get 50% of rated output if you have a bad
>diode.

Interesting approach. I'm not sure how well it will work with the
tools a GA pilot has.

A real clamp-on DC ammeter is a rather specialized tool. The usual
ones are AC -- the clamp makes a 1-turn transformer out of the wire
you are around. It may or may not read on dc-dominant paths; I can
see the trasformer getting saturated and/or only reading accurately
on balanced waveforms.

Hmm, it should be possible to use a DVM in AC mode on the
alternator output. Fair-good DVM's are really inexpensive.
A True RMS one would tell you in a second. But it would take
some experimenting to say what AC voltages would mean "yes,
you DO have a bad diode."...

--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

The clamp on amp meters that read DC and AC current use a Hall effect
IC. I bought one on Ebay for $60 over a year ago.
Most run of the mill clamp on amp meters use a transformer which will
only read AC.

On Tue, 7 Dec 2004 06:16:02 +0000 (UTC), David Lesher
<wb8foz@panix.com> wrote:

>John@no_where.com (John_F) writes:
>
>>Find or purchase a clamp on amp meter that will read both AC and DC
>>amps. Turn on enough loads so that the alternator is generating at
>>least 50% of it's rated load. Measure the DC amps and the AC amps of
>>the alternator output. The AC current should not exceed 15% of the DC
>>amps. If it exceeds 15% then you have a bad diode or stator winding.
>>In many cases you can not get 50% of rated output if you have a bad
>>diode.
>
>Interesting approach. I'm not sure how well it will work with the
>tools a GA pilot has.
>
>A real clamp-on DC ammeter is a rather specialized tool. The usual
>ones are AC -- the clamp makes a 1-turn transformer out of the wire
>you are around. It may or may not read on dc-dominant paths; I can
>see the trasformer getting saturated and/or only reading accurately
>on balanced waveforms.
>
>Hmm, it should be possible to use a DVM in AC mode on the
>alternator output. Fair-good DVM's are really inexpensive.
>A True RMS one would tell you in a second. But it would take
>some experimenting to say what AC voltages would mean "yes,
>you DO have a bad diode."...

John@no_where.com (John_F) writes:

>The clamp on amp meters that read DC and AC current use a Hall effect
>IC. I bought one on Ebay for $60 over a year ago.
>Most run of the mill clamp on amp meters use a transformer which will
>only read AC.


I've not seen a Hall Effect meter near that cheap. [When I last used
on, such was a multi-thousand $$ Tek probe...] That will work on DC
as well as AC.
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433