Aircraft Fuel Level measurement

Good day to all, my team and i are currently doing a project to measure aircraft fuel laboratory trainer as our final year project.

To cut things short, we have done our first part of changing the capacitive reading to a frequency reading using a circuit we researched on. As of now, we are stuck with converting the frequency reading to a voltage and percentage reading. We have yet to find a program to measure our frequency input(was using a analog in program and we realized our frequency input is digital). As of now we want to try the frequency count example: http://www.pjrc.com/teensy/td_libs_FreqCount.html

May i have some advise if I am in the correct path already or there should be some other methods used? Replies much appreciated ;D

may I suggest you add frequency counter to the subject line ?

Perhaps a hardware solution like an LM2917 frequency to voltage converter?

dave-in-nj: may I suggest you add frequency counter to the subject line ?

bluejets: Perhaps a hardware solution like an LM2917 frequency to voltage converter?

We initially wanted to use LM331 frequency to voltage but somehow we did not get the circuit to work even with the help of our project supervisor and thus we want to use the arduino program to help us do this function instead.

dave-in-nj: may I suggest you add frequency counter to the subject line ?

As in the frequency counter program from the website i posted?

Probably because the LM331 is a voltage to frequency converter....

It says that lm331 can convert frequency to voltage too. But our main concern is to use arduino instead of and IC chip to convert frequency to voltage too :D

Headless20:

dave-in-nj: may I suggest you add frequency counter to the subject line ?

As in the frequency counter program from the website i posted?

What do you mean by this? And what do you think @dave-in-nj meant by his suggestion?

Are you really in your final year?

If you modify the title of this Thread to include the words "frequency counter" you should catch the attention of people who know how to do that. Most people here know nothing about aircraft fuel tanks and will just ignore this Thread.

...R

The LM331 is a precision V - F converter using linear technology. LM331 PDF data sheet

If you want to use it in F - V mode, did you check the output voltage swing available, considering you can only go from 0 to 5V into a standard Arduino, but you don't detail what Arduino you use. Give details. I assume you will be using pin 1 of the LM331 as your output, which is the output of a current switching transistor. You'll need to do some nice smoothing on that, maybe even an additional op-amp, before you can connect that to the Arduino. But, alas, you do not give details.

You say you have a capacitance measuring system providing a frequency output, correct? You don't detail anything else about it, such as what the frequency range is, are you talking 50Hz, or 20kHz, or 1MHz? What about the duty cycle of the waveform, is it 50%, 10%/90%? Is the change in measurement giving a linear change in output frequency, do you have any clue?

Once you know this, it might be possible to simply use an Arduino to take the frequency input and then perform the calulations on it to give a representation of fuel level, without making it more complex by converting from frequency to voltage with a LM331 to then convert back through a 10 bit ADC.

My thought is that using a LM331 is just the wrong thing to use for what you want to do.

Anyhow, you need to give more detail, which you should be good at by now in your final year I would think.


Paul