------------------------------------------------------------ Excerpt from the following link: http://www.doityourself.com/stry/how-does-an-analog-voltmeter-work
An analog voltmeter works by passing a current through a coil that is suspended between two permanent magnets. This coil of wire is known as a moving coil since it moves in relation to the permanent magnets when a voltage is applied. When a voltage is applied and the voltage scale is chosen, a resistor of known value is placed in series with the measurement leads. This way Ohm's Law can be applied. The applied voltage through the coil creates a magnetic field which acts against the permanent magnets that the pointer pivot is placed between. This magnetic field causes a corresponding deflection of the pointer. This pointer deflection will be in direct proportion to the amount of voltage being applied to the moving coil wrapping the pointer pivot. Once pointer oscillation has stopped, accurate readings can be made. ------------------------------------------------------------ So to summerize: Yes Marek, basic analog meter movement is caused by current flow through the meter coil. I suppose in a a way that makes all anaolog coil meters "current" meters. I referred to the fuel gage as a voltage meter so as to suggest that with the meter completely removed from the boat a "voltage" applied across the terminals from sense to ground or sense to vcc (+12v terminal) would cause meter deflection. In order to troubleshoot one might select a common 6v lantern battery for this task. Using the attached drawing as a referance and understanding that R2 is the fuel level sender and "D" is the sender "sensing" terminal on the meter. I believe that inadvertently swapping the +12v and sense lines or swapping the ground and +12v lines would cause the symptom of the fuel gage needle pegging low. To both our points, the attached picture suggests that the meter being used is a voltage meter (Vg) and referances the current from points D to B (Ig) as driving its movement. Josh On Apr 4, 2015 10:40 PM, "Marek Dziedzic via CnC-List" < [email protected]> wrote: > Josh, > > This is certainly not sailing related, but if i remember it correctly, > they are all really ammeters (the current flowing through them creates the > magnetic field that moves the needle). > > Marek > > > > Josh Muckley via CnC-List wrote: > > All analog meters are just measuring the "voltage drop" across a > resistance. The key is to have the appropriate voltage input +12v. If the > +12v and the sensing line were reversed then the "voltage drop" would be > "negative" driving the needle to the empty peg. > > Josh > On Apr 4, 2015 7:08 PM, "Wally Bryant via CnC-List" <[email protected]> > wrote: > > I thought they were Ohm meters. Anyway, I just Googled it to make sure, > and see a ton of pages on testing marine fuel sender resistance. > > Wal > > you wrote: > > I agree with your diagnosis. It's gotta be reversed polarity...of the > sense and gnd. Fundamentally the fuel gages are just voltage meters. They > respond proportionally to the voltage drop across the variable resistance > in the sender. I would disconnect the leads and use an ohm meter to > measure and validate the resistance of the senders. Switching the polarity > of the sense and gnd monetarily probably won't break anything. Before > doing so validate that your wiring looks like the attached picture. > > > > _______________________________________________ > > Email address: > [email protected] > To change your list preferences, including unsubscribing -- go to the > bottom of page at: > http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com > > > _______________________________________________ > > Email address: > [email protected] > To change your list preferences, including unsubscribing -- go to the > bottom of page at: > http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com > > >
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