The Danger of Thermocouples from Dodgy Sources

18 Aug 2022

Due to the current shortages of parts, and the escalating costs, I decided to skimp a little and buy a bunch of thermocouples from AliExpress, because I needed quite a few for testing a couple of projects.

Unfortunately, they will all need to be carefully disposed of.

I got an inkling something was wrong when I picked them up. Within seconds, my hand felt itchy.

I took a microscope to the thermocouples, and saw this : (

There were loads of fibres! The blue thread thermocouple was from AliExpress. For comparison, the green thread thermocouple was from a normal distributor. The green one has its fibres impregnated with heat-resistant material, and has no fibre strands poking out.

I put the AliExpress one over a flame for 10 seconds or so, and some fibres were still visible, so I suspect they are glass, and not plastic. The photo below shows the after-flame result.

I washed hands, and in desperation applied a load of impact adhesive to my hand, let it dry, and then peeled it off. I don't have an itch any more. I'm not recommending this procedure since I am not a doctor, but I'd be interested to know what others would do in such a situation.

Parents

dougw over 3 years ago

If you need to use them, maybe wrap them in Kapton tape and handle with care.

Maybe remove the insulation and replace it with some other sheath.

I have some plastic insulation tubing that would work for sections that don't get too hot.

Even heatshrink sections that don't get too hot.

Silicone coating?
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shabaz over 3 years ago in reply to dougw

Good ideas, I had five of them each 2m long so I felt it was a waste of Kapton tape and binned them. I got some alternative plastic ones next-day from Farnell, they are still not really what I want, but they were lower cost than I expected, and will do for now for testing.
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shabaz over 3 years ago in reply to dougw

Good ideas, I had five of them each 2m long so I felt it was a waste of Kapton tape and binned them. I got some alternative plastic ones next-day from Farnell, they are still not really what I want, but they were lower cost than I expected, and will do for now for testing.
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