I had a feeling my blasting cap experience would side track the article, but it was interesting. The wiring was not a problem as the tester was located near the end of the machine and all wiring was direct from the tester to the test fixture. The system actually tested multiple devices at the same time (as I recall, it was 8 at a time), and no they were not series connected, it actually ran separate current sources for each device.
Interesting about the blasting cap tester. I always wondered about them.
But my guess is that you found a real challenge getting the machine builders to carry the four wires all the way to the test fixture. I have done a few four wire resistance checking machines and the wiring crew always wanted to tie those conductors to each other way back in the electrical panel. It was even a challenge keeping the wire numbers separated. What we arrived at was adding letter extensions to the wire numbers, -A, -B, and so on. But it required constant attention to make sure that no "simplifications" were done. And there were a couple of times when the engineering manager had to back me up.
Interesting story, brings back memories of a project many years ago where I designed and built a dedicated 4 wire ohm-meter for testing blasting caps on a production line. Not only did it have to be 4 wire for the low resistance but it had to have a testing current source guaranteed to stay well below the "firing current" from the very moment of connection, no inrush spikes or anything. Needless to say, I didn't design the "clips", they were part of an automated machine.
Steve, your idea is brilliant. Over the years I have seen a commercially made clip quite similar, but made just for that purpose. The humble spring clothespin would be a very good basis for the same function, and using the adhesive backed copper foil is a great idea, which beats the dimes glued on with epoxy, although it may have more of a corrosion issue.
I sell calibrated clothes pins that can be used for this application for only $19.95 each. They are ready to go as soon as you have filed them flat and added the copper and connector. Sounds like a good deal for me, er, you... :-)
I also have a special on calibrated toilet paper centers and individual sheets of paper towels.
Digital healthcare devices and wearable electronic products need to be thoroughly tested, lest they live short, ignominious lives, an expert will tell attendees at UBM’s upcoming Designers of Things conference in San Jose, Calif.
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