When I started my degree in Control Engineering deep in the mists of time circa the mid-1970s, the only computer that was physically located in the engineering department was analog in nature (we also had access to a digital mainframe located in another building that we programmed using perforated paper products in the form of paper tapes and punched cards).
As I recall, our analog computer was similar to the beast shown in the image to the right. This unit was formed from lots of small modules, each of which provided a single analog function, like being able to compare, add, subtract, multiply, and integrate analog signals. We connected the various functions together using cables with jack plugs on each end.
Although this may seem equivalent to stone age technology to younger readers, you can actually do some amazing things with an analog computer, like modelling dynamic systems with gusto and abandon (and aplomb and panache, of course).
By some strange quirk of fate, I recently came into contact with an analog-related topic because I was pondering the concept of applying dither to analog signals to increase the effective number of bits on an analog-to-digital converter (ADC). As part of this, I ran across the fact that one of the earliest applications of dither occurred in the mechanical analog computers used in airplane bombers in World War II.
As we read on the Wikipedia (quoted from Principles of Digital Audio by Ken Pohlmann): “Curiously, these computers (boxes filled with hundreds of gears and cogs) performed more accurately when flying on board the aircraft, and less well on ground. Engineers realized that the vibration from the aircraft reduced the error from sticky moving parts. Instead of moving in short jerks, they moved more continuously. Small vibrating motors were built into the computers, and their vibration was called dither from the Middle English verb ‘didderen,’ meaning ‘to tremble.’ Today, when you tap a mechanical meter to increase its accuracy, you are applying dither, and modern dictionaries define dither as a highly nervous, confused, or agitated state. In minute quantities, dither successfully makes a digitization system a little more analog in the good sense of the word.”
But we digress… The thing is that you can only imagine my surprise and delight when my chum Jay Dowling pointed me at The Analog Thing (THAT) (although it may seem obvious, I had a little brain burp and I don’t want to tell you how long it took me to realize that “THAT” was the abbreviation of “The Analog Thing”).
The first thing I want to say is that I really, REALLY want one of these bodacious beauties. The second thing is that — if you haven’t already done so — you really should take the time to peruse and ponder this brilliant video from Veritasium.
The part where the host shows how to implement a mechanical analog for the addition of ten sine waves left me gasping in awe.
The next part — breaking apart a curve composed of multiple sine waves into its component frequencies — requires the ability to multiply the composite curve by a sine wave and then take its integral. “How on earth could anyone do this using mechanical means,” I thought to myself. All I can say here is that the mechanical integrator is a thing of beauty that brought a tear of joy to my eye. Even better, we’re only around halfway through the video at this point.
What say you? Are you as amazed by the mechanical analog creations as am I? Also, do you think you could be tempted by The Analog Thing?