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PS: I will mess up a lot of terminology throughout the question.

Anyways,

I want to build a circuit which is in the shape of a mesh, something like a table and subsequently detect whenever there is a break at one of the nodes (i.e. the intersection of vertical and horizontal wires). It will carry very little current (from a AA battery).

Can anyone help me how to execute this idea?

nerdcortex
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    @CuriousOne could you possibly stop alienating newcomers? engineering questions are welcome in Physics.SE as long as they relate to physics – lurscher Sep 13 '15 at 18:10
  • This is an engineering question. I will help you as much as to point you to LT Spice, a free professional grade circuit simulator that will greatly help you to understand your circuits: http://www.linear.com/designtools/software/#LTspice. As for a practical implementation, the usual method uses time division multiplexing with digital mux/demux circuits and diodes. If you use CMOS parts like 74HC4067 you can run the circuit for years on one battery. – CuriousOne Sep 13 '15 at 18:14
  • @lurscher: We have an off-topic category that calls out engineering questions. I did, by the way, just help the OP. What did you do except for falsely complaining about me not being helpful? – CuriousOne Sep 13 '15 at 18:15
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    @lurscher: what is the physics in The question asked, "can you help me execute this idea?" – Kyle Kanos Sep 13 '15 at 18:40

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Since lurscher thinks he is so smart but obviously doesn't care to help you with the physics of this problem, I will. Get a square tub and fill in a couple of inches of saltwater. This will simulate a dense conducting mesh. Now make yourself two flat electrodes from copper or steel that are approx. 5-10% of the width/length of the tub. Connect them to an Ohm-meter and hang them into the water on two sides of the tub. Measure the conductivity of the saltwater. Now insert a non-conducting object (e.g. a glass jar) into the water. That object has to go all the way from the bottom of the tub to the surface of the water (it should stick out). This way you have interrupted the flow of electricity in the volume of that object. Compare the conductivity between the two electrodes to the conductivity without the object. Make a number of plots of these measurements for different locations of that object. Leave the object in the middle of the tub and make a plot of the conductivity depending on the position of the electrodes. Change the non-conducting object against a bigger/smaller one. What do you see? How big is the effect as function of the size of the object?

Have fun!

This, by the way, is a perfectly valid engineering method for a number of physical problems that was in use until computers were fast enough to do numerical calculations on these kinds of problem.

CuriousOne
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  • What you describe is known as "impedance tomography" and has been used (quite recently) to determine changes in conductivity in the brain (due, for example, to blood pooling in the case of hemorrhagic tumor). Usually, at least 32 electrodes and multiple orthogonal excitation patterns are used to get sufficient spatial resolution (rather than simply "it is a break"). David Holder from UCL wrote a good introduction - there has been more recent work but I can't quickly locate it. – Floris Sep 14 '15 at 06:42
  • Yep, that's what it is, if you do it with AC currents, which requires considerable equipment and experimental skill. I have a random paper on that out there with a few other people, where we show that some of what has been done in the field by others has serious interpretation errors. If the OP decides to try this he will quickly learn just how fickle the measurement is. – CuriousOne Sep 14 '15 at 13:35