[Fran] & [Bil]‘s Dinosaur Den

DinosaurI suppose I can take credit for introducing the super awesome [Fran Blanche] to Hackaday’s very own crotchety old man and Commodore refugee [Bil Herd]. I therefore take complete responsibility for [Fran] and [Bil]‘s Dinosaur Den, the new YouTube series they’re working on.

The highlight of this week’s episode is a very vintage Rubicon mirror galvanometer. This was one of the first ways to accurately measure voltage, and works kind of like a normal panel meter on steroids. In your bone stock panel meter, a small coil moves a needle to display whatever you’re measuring. In a mirror galvanometer, a coil twists a wire that is connected to a mirror. By shining a light on this mirror and having the reflected beam bounce around several other mirrors, the angle of the mirror controlled by the coil is greatly exaggerated, making for a very, very accurate measurement. It’s so sensitive the output of a lemon battery is off the scale, all from a time earlier than the two dinosaurs showing this tech off. Neat stuff.

One last thing. Because [Bil] and [Fran] are far too proud to sink to the level of so many YouTube channels, here’s the requisite, “like comment and subscribe” pitch you won’t hear them say. Oh, [Bil] knows the audio is screwed up in places. Be sure to comment on that.


  1. misterman says:

    A galvo is an ammeter, not a voltmeter.

    Otherwise, this looks like a great start to a great series!

    • Jay says:

      It needs volts volts to get the amps flowing and the coil has a fixed resistance value. The rest is jus tOhm’s Law.

      • Greenaum says:

        Usually a voltmeter is an ammeter with a high-value resistor in series. Or a milli-amp meter, more specifically. An ammeter is a mA meter with a low-value shunt resistor in parallel. If it’s a uA meter, use a different resistor.

        The actual movements used in analogue, moving-needle meters are usually just milliammeters, with whatever arrangement of stuff around them to make them fit the purpose.

        Though, of course, you can’t have amps without volts. Volts are pushed, amps are pulled. In the case of this antique galvanometer type thing, I don’t know what it’s resistance is, and what it usually measures.

        • Greenaum says:

          Oh, talking of instruments that surely must be obsolete by now, I remember losing a lot of points in a school entrance exam, for not having a clue what a “gold-leaf electroscope” was. I know now, I’ve made them since, but I think conflicting syllabusses put the exam question before the actual teaching..

      • AussieTech says:

        The deflection force is directly related to the current flowing and only indirectly related to the voltage across the coil (via Ohms Law).

  2. r4k says:

    The unintentional reverb is *far* less annoying than the intentional music in the background.

    Not entirely surprising after the annoying video in the background during the opening sequence.

    I’m sorry, but there is no way I can put up with this for 60 minutes.

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