How to measure diesel tank level by pressure sensor, tank area and diesel paramenters

Hi.

I have two diesel tanks here, used both in trucks and buses, they have around 250 liters of diesel when full filled (250 liters capacity). They have retangular format.

I want to make an electronic measurement to them, of how many liters of diesel is present inside them, using these parameters:

- Pressure measure (in PSI), obtained from an electronic sensor placed at the internal bottom of theses tanks.
- Tank base area (if really needed to use it in the equation)
- Data from the diesel (density and other necessary paramenters)

The diesel tanks have these dimensions:

Base dimensions: 125cm x 60cm
Height: 40cm
OBS: 1cm (centimeter) = 2.54 inches


All I need to know is what would be the aproximate pressure measurement given by the sensor, in PSI (pound per inch) [the measurement unit may be other, I could convert between them], when the tank is nearly filled and nearly empty. I am stuck on this doubt because the selection of a electronic pressure sensor (dedicated IC) will be based on its pressure measurement range (Ex: 3 to 50 PSI, or Ex 10 to 150 PSI, or Ex 0 to 1.5PSI).

EXAMPLE:
What would be the approximate pressure measure when the tank is nearly filled?
What would be the approximate pressure measure when the tank is nearly empty?

Example os pressure sensors:

1) BMP085 from Bosch -> range from 4.35 to 15.95 PSI - http://search.digikey.com/us/en/products/BMP085/828-1005-6-ND/1987016

2) MPX2202 Series from Motorola -> range from 0 to 29 PSI - http://search.digikey.com/us/en/products/MPXM2202AS/MPXM2202AS-ND/420527
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3) MPXV5010 Series from Motorola -> range from 0 to 1.45PSI - http://search.digikey.com/us/en/products/MPXV5010GC7U/MPXV5010GC7U-ND/412949

4) MPX5100 Series From Motorola -> range from 0 to 14.5 PSI - http://search.digikey.com/us/en/products/MPX5100GP/MPX5100GP-ND/464061

There are many ICs models available with different measurement ranges.
All I need to know is what is the aproximate pressure present at them bottom of the tank when it is 100% filled and nearly empty. The tank has 250 liters capacity and retangular format. Base dimensions of 125cm x 60cm and height of 40cm.

I am looking for this range of pressure values, in any measurement unit, PSI, KpA, mbar, atm, etc

Somebody may help about this question?
Some better ideias to measure diesel level (in % or in liters directly) in the tanks? I don't want to use a capacitite or ultrasonic transducer method to measure the levels.

Thanks in advance.

The density of diesel is given as 0.832. Thus, a column 10 cm high will exert a pressure of 8.32 g/cm^2.

John

Hi.
Could you convert this measurement unit (g/cm^2) to PSI?
Big thanks for the help. *** bless you

1) (2.54 cm/in)^2 = 6.45 cm^2/in^2
2) Thus, for the 10 cm column, (8.32 g/cm^2)x(6.45 cm^2/in^2) = 53.66 g/in^2
3) To convert g to #, divide by 454g/#
4) 53.66g/454= 0.118# and 53.66 g/in^2 = 0.118 #/in^2 or psi
5) Now, that is for a column that is 10 cm tall. A column 10" tall would exert 2.54 times that or 0.300 psi

John

Hi.

If the pressure exerted by the diesel is around 0.832 g/cm^2. A tank with 40cm height will give me a maximum of 33.28 g/cm^2.

Using this online converter: http://www.sensorsone.co.uk/pressure-units-conversion.html , 33.28 g/cm^2 = 0.47 PSI.

So I think "MPXV5010 Series from Motorola -> range from 0 to 1.45PSI" is suitable to measure diesel level of these tanks, considering this unit conversion I did wasn't wrong.

I used more three online unit converters to convert 33.28 g/cm^2 to the PSI unit and all of them gave me a value of 0.47

Please correct me if I am wrong

---------- Post added at 05:04 ---------- Previous post was at 03:48 ----------

Now my doubt is if this sensor is resistant to diesel oil. I could insulate the sensor from the diesel using some adequate resin, but anyway i don't know if that's possible

See https://cache.freescale.com/files/sensors/doc/app_note/AN3728.pdf

Keith