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I am currently working on a project and would appreciate your help. So i have this fence (eg. 3m x 3m) on which my 3 axis accelerometer is mounted in the geometrical center. It can detect whether someone is trying to climb upon it, or if someone's hitting or trying to break it using brute force. The deal is, suppose a person tries to cut the fence at the bottom left corner. Assuming that this will produce much smaller vibrations, how could one detect whether someone has cut the fence or not, using the accelerometer or any other sensor ?

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closed as off-topic by Chris Stratton, Voltage Spike, Bimpelrekkie, Finbarr, alex.forencich Jun 6 '18 at 7:08

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  • \$\begingroup\$ Is the fence indoors so that it is shielded from the wind? \$\endgroup\$ – Andrew Morton Jun 4 '18 at 12:32
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    \$\begingroup\$ I'm voting to close this question as off-topic because it is about algorithms for event detection, not electrical engineering. It is also far too broad to fit the stack exchange model. \$\endgroup\$ – Chris Stratton Jun 4 '18 at 13:56
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how could one detect, whether someone has cut the fence or not, using the accelerometer or any other sensor or electronic device.

If you threaded a "sense" wire that snaked left to right and from top to bottom and made that wire look like part of the fence, it's likely that someone cutting the fence will also cut the sense wire and this can be detected by a circuit quite easily.

The general idea is embodied in this type of product but it's quite easy to make your own: -

enter image description here

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  • \$\begingroup\$ That would only detect someone very careless or trying to bring a vehicle through. A wire cutters approach would just make a flap for crawling under one of the inverted V's. Even if color matched, the wire won't look like part of the fence since it's an extra element in an otherwise regular pattern. \$\endgroup\$ – Chris Stratton Jun 4 '18 at 13:57
  • \$\begingroup\$ @ChrisStratton the picture is an example of the method. My suggestion is to use a threaded sense wire snaking left to right and top to bottom. And there is no reason why this would not work with a the type of interleaved fencing that has insulated/coated wires. I disagree with you. \$\endgroup\$ – Andy aka Jun 4 '18 at 14:18
  • \$\begingroup\$ It's still dead simple to identify any "extra" added to the very regular pattern of the fence wire. And probably to defeat it with a clip lead. This proposal really only works against the very careless. \$\endgroup\$ – Chris Stratton Jun 4 '18 at 14:22
  • \$\begingroup\$ I'm not saying it is infallible of course. \$\endgroup\$ – Andy aka Jun 4 '18 at 14:24
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This is quite a broad subject. The 'Any electronic device' can be anything from a simple mechanical vibration sensor to an optical fiber replacing the fence's thread.

Obviously, there is cost involved and tons of other requirements which we don't know.

Look at some of the security fence vendors such as Magal security systems for more information.

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  • \$\begingroup\$ That's true, the question is indeed problematic. But this is a comment, not an answer. \$\endgroup\$ – Chris Stratton Jun 4 '18 at 13:58
  • \$\begingroup\$ If link-only answers aren't allowed, then adding a link to a non-answer doesn't make an answer either. \$\endgroup\$ – Chris Stratton Jun 4 '18 at 21:09

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