@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

@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 :)

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