Sensor for detecting the presence of jacketed wire

  • Hello, I'm working on something that requires sensing the presence of insulated wire. I'm doing a life-cycle test on a device with a moving wire, and if this wire breaks, I need the sensor to be alerted to this fact. But since it's a life cycle test, we want a no-contact sensor, to reduce wear on the wire.

    We tried inductive sensors, but the wire is so thin that they aren't working! The wire is awfully thin so I'm not sure if light would work much better.

    Any creative ideas? Thank you all

  • Mod

    @alec44 is the wire conductive?

  • @Yveaux Yes but we can't cut the coating at all. So if you were thinking of using it to complete a circuit, I don't think that'd be feasible. I had that idea too 🙂

  • @alec44 Induction ? Pressure switch with a roller ?

  • @alec44 We need a little more information.

    Is it flexing or axial movement - rotation, or translation? How fast, how much, and how often? How long is the wire? Is it moving along its entire length? Is it a single wire or a multi-wire cable? Is it in an inaccessible environment, or can it be moved for testing? Are there temperature, pressure, optical or chemical environmental considerations? What is it connecting? Can the circuit be altered at all? Is it possible to inject signals at one end and detect them at the other? What signal (voltage, current, frequency) does it carry now, and does it need to carry them for the life cycle test? How thin is the wire? What structures are near the wire, and can they be modified? How precisely do you need to know the point of failure (e.g. "101 273.27 flexions" vs "more than 100 000, fewer than 110 000")?

  • @gregvp Hi gregvp, thanks. The wire moves both axially and radially. It is being reeled and unreeled continuously. About 100 inches per second axially, much slower radially. It moves about 30 feet, close to its full length. It is a stranded wire, about 1mm thick. It's in a very accessible place. No such big environmental considerations. It doesn't connect anything, everything can be altered except the wire itself. It is not possible to inject a signal because I can't cut into its protective coating, just to avoid the coating stripping off during such a long test. It doesn't carry any signal, it's just part of the physical device. It has an aluminum testing apparatus that we can alter in any way. We just need to know when the wire breaks, if it ever does.

    Thanks for your interest in this problem. I'm hoping this helps give people any ideas that might be feasible. I think we might try a laser but I'm concerned the receiving window will be too small. We'll see though

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