IMSAI Guy's Contact-Free Oscilloscope Probes Are Built for the Low, Low Price of "Nothing"

With nothing more than a short length of insulated wire, a normal oscilloscope probe can be upgraded for contact-free use.

Gareth Halfacree
1 month agoDebugging

Pseudonymous YouTuber "IMSAI Guy" has offered a guide to building your own contact-free oscilloscope probes — which, he claims, can be made for the grand sum of zero dollars.

"It costs nothing, okay, absolutely free, free, free, free," IMSAI Guy claims of his probe design. "You can build one of these super, super easy, and like I said, it costs you nothing ta all — and then you can probe around a circuit and not make contact [with] it."

A non-contact probe is handy for a range of tasks, not least of which is experimenting with high-voltage power supplies — the sort of thing that might short an oscilloscope, melt a probe, or worse if you make contact somewhere you should not. With a non-contact probe, that's not a problem — and, as IMSAI Guy shows, they can be made surprisingly easily.

If you want to experiment with contact-free oscilloscope probes, you won't find cheaper than these. (📹: IMSAI Guy)

"[I took] an insulated wire and I put some large coils on this end," IMSAI Guy explains, pointing to a now coil-filled area in front of a commercial oscilloscope probe's tip, "and some small coils on [the other] end so it slips right on the end of your oscilloscope probe."

Assuming that you have insulated wire lying around, and that you've already got a contact-based probe for your oscilloscope, the build is indeed free — and yet effective. "Another use case might be that you want to probe an oscillator circuit, but the act of actually probing the circuit adds capacitance to it and you may disturb what's going on there," IMSAI Guy adds. "We can just reach in here with this little probe and we can see what's going on."

The full guide is available in the video embedded above, and on IMSAI Guy's YouTube channel.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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