(First of all, apologies for the many "uhhh"s and "ummm"s you can hear - no idea what was going on there. Edited out a lot, and next time it should be better.)

Topics this time are my effort so far for the RetroChallenge 2018/04 (25% in), a short and biased discussion of some available handheld oscilloscopes, disassembling consumer-scales to see what was going on inside, hacking together a small digital probe to distinguish high/low/floating pins, and blowing a fuse while poking at electronics.

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Links/show-notes, in that order:

• my effort this week for the RetroChallenge 2018/04 (April)
• some portable scopes:
  • the ones I used:
    • Velleman HPS140i (1-channel)
    • Velleman WFS210 (WiFi, 2-channel)
    • Seeedstudio DSO Nano v1 (1-channel)
  • nice but starting from approx EUR 400:
    • Owon HDS series
    • Micsig tBook series
    • Siglent SHS series
  • PC-based:
    • Owon VDS series
    • LabNation SmartScope (software any good..?)
• Awesome Space retro-place (Utrecht, NL)
• Makersbase fablab (Breda, NL)
• Hackalot hackspace (Eindhoven, NL)

W.r.t the blown fuse: I made the rookie mistake of connecting probe-ground to something main-referenced (but not earth)... #makeagoodfirstimpression

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Some pics of scales-disassembly:

(load-sensor mounted in one of the scales' 4 feet)

(strain-gauge element (?) embedded in metal spring-thing)

Note that when the metal thing is flexed, both "halves" of the element would decrease in resistance - a few hundred Ohms when flexing them by hand. That's why I don't understand why there were 3 wires bonded to this thing. Why not use 2? (From what I read and discussed with a friend, one "half" would ideally have to have a constant or at least less-decreasing-when-flexed resistance, to be used in a Wheatstone bridge.)

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Schematic and pics of the digital probe:

(probe in a blob of hot-glue)