I have conducted a experiment to measure water displacement using a variable resistor. However i am now stuck, is there a equation to convert resistance into water displacement. i also have the water level im ml. any help would be much appreciated, thanks alot, hwk

your posted method isn`t quite clear, how is the VR employed?

I`m picturing a floatation device on the end of an arm attatched to the VR (potentiometer), would this be about accurate?

This sounds like a calibration problem. Why don't you measure the resistance at many displacement points and plot it? Should give you a rough idea what the curve would look like. Then you can do a curve fit to some type of equation thats similar.

From what I read I'm imagining a device which measures resistance between the water at the bottom of a tank and the surface of water. The higher the resistance the more water there must be, because there is more water for the electricity to go through more water registers as more resistance.

 

He wants to take his resistance reading and use that to calculate the the height of the water. Is that right?

 

If so the best idea would be to just take multiple readings and work out the relationship between resistance and height. Once you have the relationship you'll have a formula with which you can convert resistance into height of water.

if he's adding stuff to the water the resitivity of that will effect the voltage reading in that case....

YT2095...yes thats how i have measured the water level. What i have done is started with a set amount of water (say 200ml) then added cubes of metal to this water (i have recorded the area of each cube), Then i have measured the difference in resistance each time i put a cube in. hope this makes more sense.

 

Hwk

Plot resistance against displaced volume, the function of the graph will yield the equation... If your lucky it'll be a streight line and you can use y=mx+c

Kalynos pointed out a potential problem of what being added will affect resistant. The way around this is have an overflow into a secondary tube where the resistant will be measured. AN overflow is also a very low tech way to always have the same starting height or volume in the displacement tank. Just pour fluid in until it overflows, then add your stuff. If you can, use two or three valves, one between the overflow tube and the displacement tank. One at the bottom of the overflow tube. And maybe a third between the bottom of the overflow and the bottom of the displacement tank. You can either drain the overflow tube between experients with the drain valve of the overflow tube, or you can open the bottom connector value and blow into the top of the overflow to recycle the water. Keep the overflow tube vented so it does not airlock.

Kalynos pointed out a potential problem of what being added will affect resistant. The way around this is have an overflow into a secondary tube where the resistant will be measured. AN overflow is also a very low tech way to always have the same starting height or volume in the displacement tank. Just pour fluid in until it overflows, then add your stuff. If you can, use two or three valves, one between the overflow tube and the displacement tank. One at the bottom of the overflow tube. And maybe a third between the bottom of the overflow and the bottom of the displacement tank. You can either drain the overflow tube between experients with the drain valve of the overflow tube, or you can open the bottom connector value and blow into the top of the overflow to recycle the water. Keep the overflow tube vented so it does not airlock.

 

The post to which I replied has been shown to be an incorrect interperatation of his description due to his last post. :\