

| Subject: | Re: ammeter question |
| From: | Michael Elliott |
| Date: | Mon, 19 Mar 2007 23:24:20 -0700 |
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
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