Analog Computer Museum


Definitions

Computer - A machine that caculates.

Analog computer - A computer that performs mathematical operations in a parallel manner on continuous variables. The components of the computer are assembled to permit the computer to perform as a model, or in a manner analogous to some other physical system.

Mechanical analog computer - An analog computer with input and output usually expressed as shaft postion or degrees of shaft rotation.

Electronic analog computer - An analog computer with input and output usually expressed as direct current voltages.

Hybrid computer - A computer with both analog and digital computing elements interconnected.

What are Electronic Analog Computers

Electronic analog computers may seem to be "simple" or "like a toy computer", in fact they are powerful tools that were used during the 1950s and 1960s to design and test systems like ICBMs, supersonic aircraft and spacecraft. But the analog computer can be used to model any physical system that can be described by mathematical formulas, even more mundane ones from modeling the effects of pollution on the fish population in a river to fine tuning the suspension on a new car design. Analog computers will not only test a fixed design but also allows variables to be quickly changed to test "what if" conditions. By scaling time as an independent variable, physical processes that happen quickly can be stretched out, and processes that happen over a long period can be shortened to make the process easier to study. And it is very easy to study variables at any point in the program while it is running to find faults in the program design.
Although the electronic analog machine is correctly termed a computer, it does not perform its computations by numerical calculations as does the calculator or the digital computer. The analog computer performs mathematical operations on CONTINUOUS variables instead of counting with digits. Positive numbers are represented by positive voltages and negative numbers are represented by negative voltages, all scaled to the computerís working range, usually -100 volts to +100 volts (vacuum tube) or -10 volts to +10 volts (transistorized), Thus the analog computer does not subtract 20 inches from 45 inches to obtain 25 inches but, rather, it subtracts 4 volts from 9 volts to obtain 5 volts. This 5 volts the operator reads as 25 inches in accordance with his arbitrarily specified "scale factor" of 1 volt equals (or is ANALOGOUS to) 5 inches.
The electronic analog computer is basically a set of building blocks, each able to perform specific mathematical operations on direct current voltages and capable of being easily interconnected one to another. Some of the basic operations include addition, subtraction, multiplication, division, inversion, and integration. By interconnecting these building blocks, mathematical equations are modeled. BUT an analog computer is a true PARALLEL computer that can solve one or one thousand equations at the same time. In fact, similar analog computers can be easily connected together to increase their computing power. When you think about the result of many equations being solved simultaneously and becoming the input to other equations, and sometimes these solutions are then fed back or looped back into the original equations with all of the variables changing CONTINUOUSLY with time, then you can get a brief glance into the incredible power of these computers. Output is usually a voltmeter, oscilloscope, or plotter.
Many universities today like Massachusetts Institute of Technology, University of Illinois, University of Notre Dame, and Purdue University offer classes or do research using analog computers, because they realize that the last chapter of the history of analog computers has not being written. Itís an ANALOG universe and analog computers are a natural way to study and understand it.


Some Analog Computer History

87 BC Antikythera mechanism constructed on the island of Rhodes.
70 BC Antikythera mechanism losted in shipwreck off the island of Antikythera.
1621 William Oughtred invents the slide rule.
1814 J. A. Hermann invents the planimeter.
1854 Amsler invents the modern polar planimeter.
1878 Lord Kelvin develops the "Harmonic Synthesizer".
1927 Vannevar Bush begins the design of his Differential Analyzer.
1931 Vannevar Bush's first large scale differential analyzer ("Product Integraph") is completed.
1935 Vannevar Bush constructs the second version of his differential analyzer.
1942 Vannevar Bush constructs the Rockefeller Differential Analyzer.
1946 George Philbrick founds George A. Philbrick Researches Inc.
1949 Bill Phillips builds the financephalograph liquid analogue computer.
1952 George A. Philbrick Researches introduce the first commercial operational amplifier.
1956 The Heath Company introduces the Heath Analog Computer
1960 The Heath Company introduces the Heath Educational Analog Computer Model EC-1
1964 Electronic Associates Inc. introduces the Model TR-20 analog computer
1966 Teledyne Inc. acquires Philbrick and Nexus, creating Teledyne Philbrick Nexus
1966 Ed Thorp and Claude Shannon invent the first wearable computer at MIT, to predict roulette wheels.


The Antikythera Mechanism

The Antikythera mechanism was built by an unknown craftsman and used to display the synodic months (time between new moons) of the year. To calculate this they had to develop a gear ratio of 235/19 which has an accuracy of 1 part in 40,000 to the true value.

The Antikythera mechanism also needed a differential gear in order to work and this is the first example of such a gear. (Note: The differential gear was not reinvented until 1877, 1,964 years later.)

"Gears from the Ancient Greeks" by E. Christopher Zeeman


William Oughtred

English mathematician and clergyman William Oughtred invented the slide rule in 1621, based upon Napier's logarithms.


Lord Kelvin

William Thomson (Lord Kelvin) working the integrating mechanism that his brother, James Thomson, had invented, conceived the idea of connecting these devices together to solve differential equations in 1876. Lord Kelvin used the integrators to built the "Harmonic Synthesizer" in 1878 to predict tides.


Vannevar Bush

Bush's 1942 computer ("Rockefeller Differential Analyzer") weighed 100 tons and contained 2000 vacuum tubes, thousands of relays, 150 motors, and 200 miles of wire. http://www-eecs.mit.edu/AY95-96/events/bush/photos.html

He also inspired Ted Nelson and Doug Engelbart by describing "hypertext" in his 1945 "As We May Think" article. http://www-home.calumet.yorku.ca/mbernier/www/cosc4361/bush.htm

* MIT's first Dean of Engineering
* Director of the Office of Scientific Research and Development
* Science Advisor to President Roosevelt
* President of the Carnegie Instiution
* Urged the creation of National Science Foundation.
Events in the Life of Vannevar Bush


Financephalograph

Bill Phillips is most known for his "Phillips Curve" in Economics. But before the Phillips Curve was invented and while attending London School of Economic, Phillips was having problems understanding the economics lectures. So he sketched out a hydraulic model of the economy, then built the computer that uses water to represent money as it flows through the economy and a pen plotter to display the results.
A Liquid Computer


First wearable computer

The system was a cigarette-pack sized analog computer with 4 push buttons. A data-taker would use the buttons to indicate the speed of the roulette wheel, and the computer would then send tones via radio to a bettor's hearing aid. Though the system was invented in 1961, it was first mentioned in E. Thorp, Beat the Dealer, revised ed. in 1966. The details of the system were later published in Review of the International Statistical Institute, V. 37:3, 1969. A brief history of wearable computing


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