When you need to make very tiny measurements, even noise in closed relays can throw you off. [Marco] was able to observe this effect and wanted to build a switch that didn’t have this problem. He found a technical paper that used rotary switches operated by stepper motors instead of relays. So he decided to try making his own version. The video below shows how it turned out.
The first part of the video talks about why relays sometimes inject a tiny voltage into a closed circuit. He then looks at costly switches that would work. However, since he needed many switches, he decided to roll his own.
While this is painful, it does let you optimize for your particular application. That’s why it was important to understand why relays don’t work well in this application. Copying part of a design from a very interesting-looking switch, custom PCB switch decks arrived in the mail.
Did it work? Watch the video to find out. There was something very comforting about watching the switch rotors turn under automatic control. [Marco] reminded us that the switches look somewhat like an old auto distributor.
Measuring nanovolts isn’t for the faint of heart. With a little help, your existing gear might be able to read nanoamps, however.
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