Discussion in 'Electronics Homework Help' started by makramhajji, Jul 3, 2016.

1. ### makramhajji

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0
Jul 3, 2016
I would like to pay your attention, that we have to measure the liquid electrical conductivity via one wire.

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2. ### davennModerator

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Sep 5, 2009
I don't think that would be possible

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3. ### CDRIVEHauling 10' pipe on a Trek Shift3

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May 8, 2012
I see the word "we" which appears to be homework. Regardless of that issue I think you need to explain in greater detail what your instructor wants from you. I can't help but think that it's not actual conductivity measurement (measured resistive value) but rather a 'Yes the liquid has reached a level to trigger the circuit or it hasn't. The only way I can see that happening with a single wire is if the tank is metal and buried in wet ground.

On the other hand an Antenna can appear to be a single conductor, though they aren't really. So how about thinking in those terms. IE a tightly coupled oscillator to and antenna wire would both pull the oscillator frequency and suck down its output as well when submerged in conductive liquid. In fact I would expect both freq and output changes to be measurable as the liquid gets closer to the antenna wire. Especially if the wire is oriented parallel to the liquid's surface.

Actually just musing over this assignment does stir the imagination. I'm sure your instructor has covered Capacitance so regardless of whether your using an Oscillator or not, try thinking in terms of a change in capacitance as the liquid rises and approaches a wire running parallel to the liquid's surface. A metal plate connected to the end of the single conductor would be better though.

Chris

4. ### Mongrel Shark

260
18
Jun 6, 2012
This is an old one but a good one.
One wire? Is duel core expressly forbidden?

As Chris suggested. Capacitance is the key. Think variable Leyden Jar...

The 2 wire method is best. Some testers are stricter on the interpretation of one wire. One wire in the container is easy if you can stick a bit of conductive tape on the outside. If you can only have one wire core leave the circuit its harder...

As long as the container is at the same distance from ground. Its capacitance with ground (container is one plate, ground the other) will be fairly constant. But what if you can't get a wire from your circuit to ground? You could put a "Ground Plate" in your project box. As long as the distance between circuit box and container is not changed you have useful data...

Or for bonus credit you could go with the no wires option. Optical. Shoot a laser in, measure light degradation.

Or have a magnetic float and measure inductive coupling...

There are a ton of options depending on the exact requirements. eg is the liquid specified? can I make it Mercury? or non-conductive? Do we know the specific density? can we just weigh the container? Do we have to use a wire? can we just do it wireless?Why not have a float with GPS and blue-tooth the report its height? What about air displacement? or sonar distance metering?

There are many ways to solve this problem..... Most of them involve not restricting yourself with rules that you invented by accident or because you didn't read the requirements properly....

*Disclaimer. If you get a Diploma or Degree from my help. I require you to have my name printed on your qualification next to yours to indicate how much I helped. I would also accept a portion of the qualification by post.

5. ### makramhajji

3
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Jul 3, 2016
i would like to thank you for all your suggestions
Please i think about using cell induction , we can replace the electrodes by two coils a transmitter and a receiver this is the same magnetic float and measure inductive coupling or not ?
Please how can i do ?
thank you...

6. ### CDRIVEHauling 10' pipe on a Trek Shift3

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May 8, 2012
We have a policy here at EP regarding class assignments... We don't do them. At times we'll offer suggestions to point you in the right direction. At best we may include block diagrams and or partial schematics but that it.

Chris

7. ### makramhajji

3
0
Jul 3, 2016
Please put me in the right direction
I need to make a pcb card , i don't know which component i choose

8. ### CDRIVEHauling 10' pipe on a Trek Shift3

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May 8, 2012
That's not a single wire.

Chris

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