Analogue computer

Astolabe, a special computer for star positions

Boulton & Watt engine 1788: the governor is on the right

Analogue computers are mechanical or electronic devices which solve problems. some are used to control machines. They were once the only way a machine could be controlled, and are still used in cases where digital computers are not the best choice. The abacus, a digital device also sometimes called a computer, was used by Babylonians in c. 2500 BC.

The earliest known analogue computer in metal was the Antikythera device. However, this was certainly not the first in other forms. Some people think that mental inventions count as analogue computers, such as the invention of the zero (Ancient Egypt 1700 BC). But in that case almost every invention by mankind would count as an analogue computer, and that is not really how the term is used.

Certainly the invention of the slide rule was important for calculations. They were developed in the 17th century by William Oughtred, after John Napier's work on logarithms. Slide rules are definitely mechanical calculating machines. They were the most commonly used tools in science and engineering before the 1960s/1970s.

For the industrial revolution the invention of James Watt's governor was critical, because it was a negative feedback control for large pumps and engines. In fact most analogue computers work with continuous data rather that discrete or digital data. They are like abstract models of the real world. An analogue engine models the critical aspects of the real-world engine.

Since the middle 20th century some wristwatches have had a circular slide rule built in. They were mostly used in aviation. Such a calculator is considered too technical a device for most other watch wearers. The circular slide rule has not been emulated digitally in any notable applications.

Analogue Computer Media

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  Here is an excerpt from the Bombardier's Information File (BIF) that describes the components and controls of the Norden Bombsight.

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  Main w:en:Antikythera mechanism fragment (fragment A). The mechanism consists of a complex system of 30 wheels and plates with inscriptions relating to signs of the zodiac, months, eclipses and pan-Hellenic games. The study of the fragments suggests that this was a kind of astrolabe. The interpretation now generally accepted dates back to studies by Professor w:en:Der

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  Slide rule, model Aristo 868 Studio, showing the calculation 1.3 x 2 = 2.6. Transparent background

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  Analog Computing Machine in the Fuel Systems Building. This is an early version of the modern computer. The device is located in the Engine Research Building at the Lewis Flight Propulsion Laboratory, now John H. Glenn Research Center, Cleveland Ohio.

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  1 The Heathkit EC-1 Educational Analog Computer was introduced in 1960 and could be purchased assembled or as a kit for $400. This was commonly used to educate electrical engineers in analog techniques. Photo by Michael Holley at the Computer History Museum in Mountain View, California. Taken with a Canon PowerShot A630 using existing light on November 4, 2007.

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  AKAT-1 - pierwszy na świecie komputer analogowy zbudowany na tranzystorach,

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  Analog computer application for the simulation of the controlled system with an external feedback control system based on a microcontroller interfaced as hardware-in-the-loop, with EAI-8800 analog computer, ca 1985

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  OME P2, 1952, a French electronic analog computer from Société d'Electronique et d'Automatisme (SEA)

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  The analog circuit models a string pendulum with mass = m, damping coefficient = d, string coefficient c, and gravitational force = g. It includes two integrators, each of them inverting the polarity of the input, and three potentiometers for the coefficients. For proper functioning all coefficients need to be scaled to unity.

Related pages

• Charles Babbage
• Abacus