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fuel level sensor

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t_sanoop

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hi,

i want to make a fuel level sensor..the system should be able to sense the fuel level in the tank...can anyone help me providing information about feasible fuel level sensors...whether ultrasonic sensor will be a good choice...if so can you please tell me about good ultransonic sensor system used for level measurement


thanking you
sanoop
 
hey,

describe the tank u need to monitor for fuel level...

there are many water level sensors in this forum u should search that,

but if u still need help, more details please.

cheers,
 
The use of the word "fuel" suggests combustible/flammable so caution is in order. One common way to send liquid levels involves a small tube being placed near the bottom of the tank. Gas, at some controlled rate is pushed thru the tube and bubbles out into the tank. The gas pressure in the tube is measured and is nearly equal to the pressure of the liquid at the bottom of the tank. This keeps anything that is within the tank relatively simple. The gas might be nitrogen. This is just one way - don't know enough about your situation to know if it is a good way.
 
Another way of doing this is by getting the injector pulse width.

See here.

Computing mileage on an EFI engine is as simple as totalizing the
injector ON time, totalizing distance traveled, multiply in a
conversion factor and display. Hardware needed is a Parallax BASIC
Stamp (about $50) and an LCD display board (about $90.) We use the
PWM input across an injector to grab the pulse widths. We use a bit
line to read the vehicle's VSS to get distance. We write a little
BASIC code to wrap it all together and viola! Mileage/trip meter.

There are several methods of calibrating the fuel injector flow.
The most accurate is to build my fuel injector flow bench and
actually calibrate the injectors.

(**broken link removed**)

The next best way to do this is to hook up a pulse generator (or
even better a PC using my FIT software at the above URL) to the
injector, fire off the fuel pump, discharge 20,000 pulses or so and
catch the fuel in a graduated cylinder. The pulse width should be in
the 2 ms range. This must be done instead of just yanking the
injector open to measure the flow to account for the opening and
closing delays in the injector.

The crudest but still satisfactory method is to hook the Stamp up
with some code that will display the raw injector and VSS totals,
put an accurate amount of gas in the tank, drive until it's used up
(or fill the tank, drive, fill it again and record the amount), then
compute the volume per injector pulse by dividing the fuel used by
the total number of injector firings. -John De Armond

So basically you get a microcontroller to keep adding the injector pulse width and multiply by a coefficient to get the fuel used. You can then calculate it by pushing the reset button every time your refill the tank. Use your car's manual to figure out the fuel tank volume.

But if anyone has any idea how fuel is measured in a typical car and how to read that sensor, I'm all ears.
 
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stationary tank or in a vehicle?

In general, I recommend using capacitive discharge to measure fluid level. Very simple, safe, reliable and no moving parts. It works on the principle that air and the fluid have different dielectric effects. So, the capacitance of 2 electrodes seperated by air will be less than the capacitance of those seperated by the fluid. Use the RC time constant and measure the discharge time - easy on a micro with a comparator. Or use a 555 in astable mode using the fluid capacitor as the timing cap and measure the pulse period. The period will be proportional to the fluid depth. I make my capacitive probes out of teflon wire but almost any metal will do. The advantage of the insulated wire is there is no chance of a spark (think esd).

For a vehicle, you might want multiple units to handle angles. You will also want to do some pretty good filtering as the fluid will be sloshing around.

Phil
 
philba said:
In general, I recommend using capacitive discharge to measure fluid level. Very simple, safe, reliable and no moving parts. It works on the principle that air and the fluid have different dielectric effects.

It's really not what you want to call capacitive "discharge"- that implies a strong energy burst used for fuel ignition.

Capacitive fuel meters are nice, but unfortunately I don't think they're accurate anymore for gasoline. Ethanol has a dielectric constant 10x greater than gasoline. They're now adding up to 10% ethanol to gasoline due to the MTBE phaseout, and it's not a fixed percentage either. So now the 10% ethanol/90% gasoline mixture will read twice as high as the 100% gasoline mixture.

It's possible to make a sensor that measures the dielectric constant of the liquid, it would always be 100% immersed so its reading is only of the dielectric constant and not of the level. That can be used to calibrate the level probe. This is also good because gasoline's dielectric constant does vary with temp as well, it'll compensate for it without a thermistor and additional circuitry or code.
 
well, yes, it is capacitive discharge as you are measuring the time for a capacitor to discharge. the word discharge doesn't imply a scalar value.

that's a very good idea - use a calibration sensor at the bottom of the tank. I like it. It doesn't even have to be always immersed. A uC based system could use a heuristic that would only calibrate when the probe value goes from low to high (refilling). That would be the point at which the fuel type would change.
 
Hi guys,
Has anyone tried to make a capacitive fuel level sensor?
I'm planning to make one for my motorcycle.

The idea is to make an array of capacitive sensors, so that each one is either on or off. A couple of sensors( 10 or so) implemented on a PCB would give a discrete reading of the fuel level.

Any new ideas?


Cheers,
Peter
 
Since people had mentioned capacitive fuel level sensors, I though that this might be od interest:

http://www.rst-engr.com/kitplanes/index.htm

Go down to June/July/August 2000

Other interesting avaition electronics stuff there too.

Ken
 
Capacitive gauge

I am from Brazil, and I am an Ultra light Pilot . I have a capacitive level fuel sensor which can vary between 0 pF up to 12 pF. My reader display may receive 0 volts DC up to 5 volts DC to show the level fuel on the display. I would like to know if there is someone who could give me an electronic schematic drawing to convert the capacitance ( 0 pF up to 12 pF ) in DC Volts ( 0 volts up to 5 Volts ). I will be very grateful. Sorry my English is not so good.
 
Please take a look at the pictures. It's the dismantled fuel sensor of my motorbike (pretty small (20mm x 10 mm). Top is soldered on the housing. It's On/Off and switches ground. I'm not very good in electronics and I'm wondering if this is what you guys mean with "capacitive fuel level sensor"?. Piece cost about euro 35. Is it possible to make this for yourselve?

http://www.fotopocket.nl/fpimages/2009/11/25/5b5d1e430c142035c6f2a45f8a385f68/Fuelsensor01.jpg
http://www.fotopocket.nl/fpimages/2009/11/25/4adab9f8ca18d4e8e6e6f6c9e39dab0f/Fuelsensor02.jpg
 
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