need to design circuit to monitor water level

Hi i am new here but wanted to ask for some help on something im doing for coursework

I need to design a engineering system to monitor the water level in a large water tank, using a computer. Maximum depth of tank is 4m. Indicator range must be from 0m (empty) to 4m (full). I need to use a float mechanism which needs to be connected to a potentiometer with suitable gearing.

If you could help me design this using block diagrams showing system elements firstly before designing any circuits that would be great. Also details of the circuit for the potentiometer and how the analogue signal output is linked to the computer which will be situated close to the tank.

Need feedback ASAP please in real need of some help on this and would highly appreciate it.

Regards,


Ryan

 

actually sorry have already made block diagram u can see it below (sorry dont really have time to make i block)

Float (gear mechanism) -> potentiometer -> digital input to PC -> Software processor -> visual output -> LED stack (crystal display)

If you can still help please by all means do!

 

Try an internet search on "analog to digtal converter" or "ADC"

 

What kind of liquid? You can use a pressure transducer and save yourself some headaches over using a mechanical system. You can also use optical beam bounce off of a float. I think the one that can read a bounce directly off the surface of the fluid is highly proprietary.

Pressure transducer one
http://www.circuitcellar.com/library/print/0906/Smith194/9.htm
IMHO it needs a method of checking that the tube is clear.

Oh, instead of a potentiometer this is simpler and there is no ADC needed.
http://www.scienceprog.com/using-gray-code-for-rotary-encoders/

 

you can also take a look at this attachment

moz

 

If your goal is to measure the water level at a preset level corresponding to when the tank is full and another preset level corresponding to when the tank is empty then mozikluv has provided an excellent example of such a solution.

If you need to measure the water level on a more or less continuous basis then you may what to look into technique that uses an ultrasonic transducer such as the one available from Digikey manufacturer's part number EFR-TQB40K5.

For example, if you take a plastic tube of suitable diameter and perforate it with hole along its length and then mount it vertically in the water tank and then place a floating object in the tube that is slightly smaller in diameter, you will then have a taregt off of which you can bounce the soundwave from the ultrasonic transducer. You can then use an AVR microcontroller to control the pulsing of the ultrasonic transducer and to process the return signal to determine the distance based on the "time-of-flight" of the soundwave.

hgmjr

 

If you have to use the float and potentiometer, using a 10 turn pot will make the mechanical part a bit simpler. After that, you'll need a voltage to put on the pot, and an A to D converter to track changes. How much of a change in level will influence the A to D converter quite strongly.