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Homework Help: Sensor Project

  1. Nov 1, 2005 #1
    First off i'd like to say hi guys (and gals) - this may be my first post, but should hopefully be the first of many:smile:

    Basically i have a problem regarding some physics coursework. We're actually conducting these on the 8th of November :surprised - and i have a deadline of the 20th of November. Ive decided to use a rotary potentiometer, with the aid of an attached float to measure the amount of liquid in a tank. I'll basically create your basic circuit, with an ammeter attached (multimeter to be precise) and then attach a voltmeter (multimeter..) in parralel with the rotary potentiometer. This is probably hard to visualise, but the pictures i have just spent the last 20 minutes making are to big to be uploaded :mad:

    Basically, im planning on callibrating my several potential difference readings, for the level of the water in the tank. the float will (quite obviously) float on the top of the surface of the water. So when the level is decreased, this should move the float, which should in effect turn the rotary potentiometer, which should in effect alter resistance, which should in effect alter the ptential diifferences i record. So i should be able to create a table of values (i.e. when the potential difference is X then the water level in the tank will be Y)

    Know your probably wondering why ive spent all this time typing this, but im (unbelieveably) anxious that there are some flaws in what i am doing. If you spot any, thats one reason to reply :redface: If there are any ways which i could improve this experiment, thats a second reason to reply :redface:

    The main problem i have however is the theory behind it. I dont understand/know how to explain the way i have used a potential divider (is the rotary potentiometer a form of a potential divider?).
  2. jcsd
  3. Nov 1, 2005 #2


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    Science Advisor

    A rotary potentiometer is a variable resistor. The method you are attempting has been used quite a lot. It's a sound concept. It has some drawbacks, but they are not going to effect you in your case. If you used a simple DC circuit, you can use a power supply to provide a constant current source signal to the system. As the resistance changes so will the voltage across the resistor (i.e. the level in the tank). Or you could use a constant voltage source and measure the current changes. Either way, it should work out fine.
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