Has anyone considered an electronic fuel guage based on Graham's concept that
the pressures involved are in the range of an ASI ? No repeater needed.
Motorola produces a moderate price(about $25 last I heard), linearized,
temperature compensated differential pressure transducer, the MPX5100DP, which
might do the job with only a few additional parts. The data sheet I have is
very old (1991) and shows a 15psi differential pressure unit but they may well
have a lower range by now. This unit is used in inexpensive electronic
altimeters and ASI's. The output is 0.5 to 4.5 volts for 0-15psi.The unit may
be damaged by pressures greater than 7 times rated max, which would allow
blowing into the Europa's vent to clear it without damage to the unit. Need
to verify that its plastic case is impervious to gasoline....
For fuel level measurement only the lower end of the transducer's range would
be used so it might be a bit noisy, but probably not much more than due to
fuel slopping about in the tank. A lower range transducer would be
preferable to minimize noise and maintain linearity.
As far as support circuitry, a 5 volt regulator plus an op-amp and a couple
resistors would be needed to drive a meter. A couple caps and resistors could
be added to provide damping if desired. A real enthusiast could add a
microprocessor and use it to linearize the output scale.
Sounds like an interesting project, if only I didn't need to finish building
this plane...
John A044 Newtown, CT
|