Date:         Sun, 11 Nov 2007 14:44:59 -0800
Reply-To:     David Kao <dtkao0205@YAHOO.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Kao <dtkao0205@YAHOO.COM>
Subject:      Re: Electrical Glitch causiing a dead Aux battery...more..
Comments: To: Don Hanson <dhanson@GORGE.NET>
In-Reply-To:  <001001c824b2$2a1d48c0$68b2d8d1@laptop>
Content-Type: text/plain; charset=iso-8859-1

--- Don Hanson <dhanson@GORGE.NET> wrote:

> Sony stereo draining the coach battery.  Fixed by adding a secondary switch
> in the  power lead from the extra battery.  But   here's the Oddball deal...
>
>   Many people gave me instructions on using my multimeter to trouble shoot
> stuff like current drain, etc..Well, I never could get any real readings..I
> could get DC volts to tell me the battery was down, AC amps to tell me my
> charger was on, all that kinda stuff, but no current readings no matter how
> I hooked up or turned dials, etc..  When you don't know squat about
> electrical stuff, it's hard to know if you should be getting a reading, if
> you have the probes right, if you are using the right 'scale' etc etc..
>

Normally amp meter has its own socket for the red lead probe. If you plug
the lead to the one for voltage measurement you will not get any reading for amps.
The amp meter has a near zero impedance in the meter. If you use it to measure
voltage it is a short to the circuit (battery) that you want to measure. For this
reason the amp meter on a Volt/Amp/Ohm meter has its own socket for the red lead.
I guess you have plugged it to the voltage measurement socket and that's why you
got good reading for voltage but always zero for amps. Be careful in using an amp
meter. Remember it is a short inside. You alway need to cut open a wire and put the
two leads in serial with the wire to measure current. Never use it like measuring
voltage over any two circuit points that have a voltage between the two. It would
not only damage the meter it would also damage the circuit you are trying to measure.

David




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