Well hate to argue, but I've worked and built many car's and truck's
And while the gauge was positivly fed it is typically fed off of a
simple solution that is composed of magnet wire wrapped around some
sort of (depending on age) cardboard center.  Then an arm moves up
and down via a float in the tank.  This was common in the 50's and
60's.  In the 70's they started using baffles in the tank as it was
found that the sender could (and will) change too rapidly in quick
accelerations, breaking, and tight turns.  Mid 70's to late 80's it
was common to find a solution that was closer to what you are=20
describing, but usually the tank still had some sort of baffling
system incorporated into it (look at your tank, their are these
dents in it that are very uniform) the new baffling system also
worked well to hold the tank straps at uniform positions.  Late
80's until today they use many different types of senders (thou
most are still based on the same idea) and typically the buffering
occurs either in the onboard computer (witch tells the gauge=20
where it should be) or in the gauge itself.  Want to see a perfect
example tear apart the gas tank on a VW bug some time.  Even today
if you tear down a tank their will be a float connected to a=20
plastic cylinder open the cylinder and you find a simple wire wrap
solution.  Since gas can't be ignited in its liquid state it is
completely acceptable to submerge this (usually along with the
fuel pump).

-----Original Message-----
From: Michael Rigby-Jones [mailto:Michael.Rigby-Jones@BOOKHAM.COM]
Sent: Thursday, July 17, 2003 1:58 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [OT]: Basic theory of a fuel gauge


> -----Original Message-----
> From: Jeremy Darling [SMTP:jdarling@ASKPIONEER.COM]
> Sent: Wednesday, July 16, 2003 2:15 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [OT]: Basic theory of a fuel gauge
>
> I would be willing to bet that if you pull the battery
> and then add fuel to the vehicle that the gauge would
> not move.
>
Err..probably not seeing as the gauge is electricaly driven!

        You would be correct in thinking that.  In the old days the =
tanks
were
        baffled to make the measurement more accurate.  Today they slow =
down
the
        polling of the sensor and then average it with the last few =
results
to
        create a more realistic measurement.

In the old days most fuel gauges used a hot wire movement, whose very =
slow
response time effectively integrated the senders output.

Mike


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