Mechanical Integrators (1886) | Hacker News Reader

Mechanical Integrators (1886)

books.google.com

This link is demanding that I sign up for a Google account to read the “free” book.

I suggest replacing the link to the malicious page with a link to the Archive’s scan, which is higher quality anyway: https://archive.org/details/mechanicalintegr00shaw

The instrument is called a planimeter:

https://en.m.wikipedia.org/wiki/Planimeter

Would have been very useful before computers.

They were.

https://news.ycombinator.com/item?id=16035057

Calculating a road cross section area with a planimeter would take 5 minutes top, while doing the final analytical calculation manually (but already with a programmable calculator) took - including writing down the set of operations and partial results - more like 15-20 minutes (or even more, depending on the number of points in the section).

With scientific instruments doing dynamic measurement that have always been data-heavy, something like EKG recorders, before digital data storage typically it was a paper chart recorder where there was a roll of graph paper passing under a pen.

When the signal was stable you get a straight line until some deviation then the pen moves positive or negative and draws the graph/curve in real-time.

For applications where the areas of curves above a baseline are to be considered rather than just the comparative heights, the optional mechanical integrator was available on the premium chart recorders.

There would be a second pen, connected to the integrator which followed the first pen's deviation, limited to its own small integration band of the roll paper where it would also draw a straight line in parallel to the raw baseline signal until some actual signal of interest appeared.

Then following the deviation of the first pen, the second pen produced a blip for each unit area of deviation the main pen made from its established baseline, in real time.

For a full-scale signal excursion on the main pen, in the integrator band it would draw maximum blips-per-second during the peak apex, with greater blip spacing upon the rise & fall slopes.

When a different curve having the same area was detected which had far less than full-scale readings, it would naturally be over a longer period of time, and the more slowly drawn integrator blips over that longer period would add up to the same number as the taller but equal peak had produced.

It sure beat counting the little squares on the graph paper while accomodating all the squares at the edges of the curve not fully included.

Or cutting out the curves with a pair of scissors afterward and weighing them on the analytical balance, even when using the special uniform & humidity-resistant paper intended for this purpose. However depending on the various instruments' adjustments and how the total system was operating this could give you the greater number of significant figures when it comes to data precision.

It sure was a lot quicker to just count the blips and do the math from there.

No computer necessary and you could handle far more analog data in greater detail than any accessible computer at the time.

But it was still data so you still needed fully appropriate storage and a proper file system.

> Major-General H. P. Babbage remarked that what most interested him was the contrast between arithmetical calculating- machines and these integrators. In the first there was absolute accuracy of result, and the same with all operators ; and there were mechanical means for correcting, to a certain extent, slackness of the machinery. Friction too had to be avoided. In the other instruments nearly all this was reversed, and it would seem that with the multiplication of reliable calculating machines, all except the simplest planimeters would become obsolete. [...] The author was obliged to express his disagreement with the opinion of General Babbage, that all integrators except the simplest planimeters would become obsolete and give place to arithmetical calculating machines. Continuous and discontinuous calculating machines, as they had respectively been called, had entirely different kinds of operations to perform, and there was a wide field for the employment of both. [...] No doubt the mechanical difficulties were great, but that they av ere not insuperable was proved by the daily use of the disk, globe, and cylinder of Professor James Thomson in connection with tidal calculations and meteorological work, and, indeed, this of itself was sufficient refutation of General Babbage's view.

General Babbage is none other than Charles Babbage's son [1]. He's obviously not an unbiased observer. Still, history proved him right, digital computers took over the world, while analog ones like these mechanical integrators have become historical curiosities.

[1] https://www.computerhistory.org/babbage/henrybabbage/

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