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I am using a magnetic contact sensor to detect whether the door is open or closed. The sensor will be connected to WISE-4060 module . But the question is that I will be using 300m long cable. Is is possible to use that sensor with long cable? Is that affect the sensor value significantly? What kind of cable should I choose?

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There should be no issue with a 300m loop length. The door switch is a simple ans basic magnetic reed switch contact closure. And the switch input to the Wise4060 is perfectly compatible.It would be quite unusual for there to be any problem with your proposed configuration. Unshielded twisted pair is perfectly adequate and quite commonly used for this kind of application.

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That will almost certainly work fine. The module with no wires is a permanent magnet, and the wire unit contains a reed relay which responds to the magnetic field. So the sensor simply looks like either an open circuit or a closed circuit, and that can be detected over very long distances.

The only problem I can see is the long wires acting as an antenna and playing hob with the receiver. You might even get significant RF or static charges.

Your cable should be twisted pair, and shielded twisted pair is probably good insurance. Ground the shield only at the receiver end.

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  • \$\begingroup\$ Is it ok to use unshielded twisted pair cable? Because STP is very expensive \$\endgroup\$ – fatopato Aug 23 '16 at 19:24
  • \$\begingroup\$ @fatopato - It's OK if you have no trouble. It will all depend on the amount of interference being generated locally and your sensing unit. If you do have trouble, you'll have to go to the more expensive wire, and you'll lose the investment you made in the first, cheaper wire. Your choice. You pays your money and you takes your chances. \$\endgroup\$ – WhatRoughBeast Aug 23 '16 at 20:54
  • \$\begingroup\$ Use unshielded twisted pair and loop it through a clip-on ferrite every 20 metres or so to reduce RF interference from external sources. \$\endgroup\$ – Wossname Nov 21 '16 at 10:46

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