Date:         Tue, 20 Mar 2007 06:37:16 -0600
Reply-To:     David Etter <detter@MAIL.AURACOM.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Etter <detter@MAIL.AURACOM.COM>
Subject:      Re: ammeter question
Comments: To: Michael Elliott <camping.elliott@gmail.com>
In-Reply-To:  <45FF7E14.6080603@gmail.com>
Content-type: text/plain; charset=us-ascii; format=flowed

Thanks Mike:
        What I'll do is, meter the before and after ammeter
installation voltage and just crank up the solar regulator if needed.
Volts are no problem, it's current flow into the battery that I worry
about.
        Those are the kind of figures my old physics professor would
have given me... that is after he woke me up. ;-)

Cheers!
                                        David

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>No current loss at all. Current going in would be exactly equal to
>what's coming out. The current goes through a coil and the resultant
>magnetic field moves the pointer. This does take power, which is
>caused by passing that current through a shunt resistor of a few
>milliohms, causing an eentsy weentsie voltage drop. It's common to
>see analog ammeters set up with shunt resistors such that there is a
>50 millivolt (.05 volt) drop across the resistor at the desired
>full-scale pointer reading. So for a 10A meter, the shunt would be R
>= .05/10 = .005 ohm. Power consumption at 10 amps is .05 x 10 = 1/2
>watt. Nothing to worry about. And when there is no current flowing
>(from the panel) the meter isn't drawing anything. It just reflects
>what's going through it.
>
>--
>Mike "Rocket J Squirrel" Elliott
>71 Type 2: the Wonderbus
>84 Westfalia: Mellow Yellow ("The Electrical Banana")
>74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
>KG6RCR
>
>
>
>David Etter typed:
>>Can anyone tell me if using an analog ammeter (located in-line from
>>my solar panel) would result in current loss?  It would seem to me
>>that by creating a field in a coil to operate the ammeter it would
>>perhaps act much like a choke in a normal electrical circuit.
>>        Any field offers resistance to current flow; but perhaps the
>>loss is so small....  ???????
>>
>>Thanks!
>>                                        David