The analog computers they are a type of computer that uses the continuously changing aspects of physical phenomena, such as electrical, mechanical or hydraulic quantities, to model the problem being solved.
That is, they are computers that operate with numbers represented by directly measurable continuous values, such as pressure, temperature, voltage, speed, and weight. In contrast, digital computers represent these values symbolically..
Analog computers can have a very wide range of complexity. The simplest are slide rules and nomograms, while the computers that control naval guns and large hybrid digital / analog computers are among the most complicated. At the time, they were the first computer machines developed.
Process control systems and protection relays use analog computing to perform control and protection functions.
In the 1960s, the main manufacturer was the American company Electronic Associates, with its 231R analog computer, with vacuum tubes and 20 integrators. Later, with your 8800 analog computer, with solid-state op-amps and 64 integrators.
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In the 60s 70s digital computers, based first on vacuum tubes, and later on transistors, integrated circuits and microprocessors, became more economical and accurate..
This led to digital computers largely replacing analog computers. However, analog computers continued to be used in scientific and industrial applications, because at that time they were commonly much faster.
For example, they continued to be used in some specific applications, such as the flight computer in airplanes..
More complex applications, such as synthetic aperture radar, remained under the dominance of analog computing well into the 1980s, as digital computers were insufficient for the task..
Research is still ongoing on analog computing. Some universities still use analog computers to teach control systems theory..
An analog computer is used to process analog data, such as voltage, temperature, pressure, speed, etc. It continuously stores this data of physical quantities and performs the calculations with the help of these measurements..
It is quite different from the digital computer, which uses symbolic numbers to represent the results..
Analog computers are great for situations that require data to be measured directly, without converting it to numbers or codes.
The analog computer uses the analog signal, which can be represented as a sine wave or a continuous wave, which contains values that vary over time..
An analog signal can vary in its amplitude or its frequency. The amplitude value is the intensity of the signal related to its highest point, called the crest, and its lowest points. On the other hand, the value of the frequency is its physical length from left to right.
Examples of analog signals are sound or human speech through electrified copper wire.
Analog computers do not require any storage capacity because in a single operation they measure and compare the quantities.
Analog representations have limited precision, commonly to a few decimal places.
The accuracy of an analog computer is limited by its computing elements, as well as the quality of the internal power and electrical interconnections..
It is mainly limited by the precision of the reading equipment used, which is generally three or four decimal places..
Programming in an analog computer involves transforming the equations of the problem into the analog computer circuit.
They are used to represent data by measurable quantities, such as voltages or gear rotation, in order to solve a problem, instead of expressing the data as numbers.
In monitoring and control systems they are used to determine a control formula and to calculate process parameters such as efficiency, power, performance and others..
If a mathematical expression can be assigned that defines the association of a parameter with the coordinates of an object, the analog computer can solve the corresponding equation.
For example, analog computers are widely used to evaluate the economic efficiency of power systems, and can serve as automatic regulators.
They are often used to control processes such as those in oil refineries, where continuous flow and temperature measurements are important..
By repeatedly solving the system of equations that describes a controlled process, an analog computer can scan a large number of alternate solutions in a short time. To do this, it uses different values in the parameters subject to change during the process..
The required quality can be guaranteed by means of control signals announced by the analog computer.
The values determined by the computer are transmitted to a regulating device, which adjusts the control points.
The magnitude of a disturbing or useful signal is determined using differential equations that describe the dynamic system, the values of the initial conditions, in addition to the changes determined in the statistics that measure noise and signal..
An analog computer can also be used to build instruments that automatically record disturbances and produce a control signal, which will depend on the character and quantity of the disturbances..
The simulations can be carried out in real time or at very high speeds, thus allowing to experiment with repeated runs with the altered variables..
They have been used extensively in aircraft simulations, nuclear power plants, and also in industrial chemical processes.
Most electrical analog computers work by manipulating voltages or potential differences. Its basic component is the operational amplifier, which is a device whose output current is proportional to its input potential difference.
By causing this output current to flow through the appropriate components, more potential differences are obtained and a wide variety of mathematical operations can be carried out, including addition, subtraction, inversion, and integration..
An electrical analog computer consists of many types of amplifiers. These can be connected to generate a mathematical expression of great complexity and with a multitude of variables.
Key hydraulic components could include pipes, valves, and containers.
There can be rotary axes to transport the data inside the computer, differential gears, disc, ball or roller integrators, 2-D and 3-D cams, mechanical resolvers and multipliers, and servo-torques..
- Precision resistors and capacitors.
- Operational amplifiers.
- Multipliers.
- Potentiometers.
- Fixed function generators.
Linear components perform the operations of addition, integration, sign changes, multiplication by a constant and others.
Function generators reproduce non-linear relationships. There are computer components designed to reproduce an assigned function, from one, two or more arguments.
It is usual to distinguish in this class the devices that reproduce discontinuous functions of a single argument and the multiplier dividing devices.
Among the logic components are analog logic devices, designed to separate the larger or smaller quantity between various quantities, discrete logic devices, relay switching circuits, and some other special units..
All logical devices are generally combined into one, called a parallel logical device. It is equipped with its own patch board to connect individual logic devices to each other and to the other analog components of the computer..
They are built from mechanical components, such as levers and gears, rather than electronic components.
The most common examples are adding machines and mechanical counters, which use the turning of gears to perform additions or counts. More complex examples could carry out multiplication and division, and even differential analysis.
Most practical mechanical computers use rotating axes to transport variables from one mechanism to another..
In the Fourier synthesizer, which was a machine for predicting tides, cables and pulleys were used that added the harmonic components.
It is important to mention the mechanical flight instruments in the early spacecraft, which showed the calculated result not in the form of digits, but through displacements of the indicating surfaces..
Manned Soviet spacecraft were equipped with an instrument called the Globus. This showed the figurative movement of the Earth through the displacement of a miniature terrestrial globe, as well as indicators of latitude and longitude..
They are more common, because they have a substantially wider passband and are convenient for connecting with other computers and with the control elements of a device..
They use electrical signals flowing through various resistors and capacitors to simulate physical phenomena, rather than mechanical interaction of components.
The design of the analog elements of the computer is based on direct current electronic amplifiers. These have high gain in open circuit mode.
Depending on the structure of the input circuit and the feedback circuit, an op amp performs a linear or non-linear mathematical operation. Also a combination of these operations.
This type of analog computer was widely used in computing and in military technology in the mid-20th century, such as in aircraft and missile tests..
Digital signals have two discrete states, off or on. The off state is zero volts and the on state is five volts. This is why digital computers use binary number data, in the form of 0 and 1.
Analog signals are continuous. They can be anywhere between two extremes, such as -15 and +15 volts. The voltage of an analog signal can be constant or vary over time.
That is, in analog computers, data is transmitted in the form of continuous signals. In digital computers they are transmitted in the form of discrete signals.
Analog computer circuits use operational amplifiers, signal generators, resistor networks, and capacitors. These circuits process continuous voltage signals.
Digital computers use a variety of on / off circuits, such as microprocessors, clock generators, and logic gates..
That is, the digital computer uses electronic circuits, while the analog computer uses resistors for the continuous flow of the signal..
Analog computers must deal with a certain level of electrical noise in circuits, affecting their accuracy. The circuits of a digital computer also have electrical noise, although this has no effect on accuracy or reliability..
On the other hand, the analog computer cannot produce repeating results with an exact match. This means that analog computers are less accurate compared to digital computers..
Both analog and digital computers can be programmed, although the methods are different.
Digital computers use complex sequences of instructions, such as comparing or multiplying two numbers, or moving data from one place to another..
To program an analog computer, different subsystems are electrically connected with cables to each other. For example, a signal generator is connected to a control knob, to vary the signal strength.
This famous computer was capable of storing programming instructions. With more than three meters high, the device displayed the time, the zodiac and also the orbits of the sun and the moon.
The computational part of the device thus allowed users to set the variable length of the day depending on the season. Described in 1206, this computer was very complex for its time.
One of the simplest and most recognizable mechanical analog computers is the slide rule. This is a device to approximate basic mathematical calculations.
Users slide a marked rod to align it with various marks on another rod, thus reading the device based on the alignment of those various marks.
This mechanical analog computer was capable of solving differential equations. With a design as old as the early 1800s, the differential analyzer was perfected in the 1930s and used until the mid-20th century..
It is considered the first modern computer. It weighed 100 tons and contained 150 motors, plus hundreds of miles of cables connecting relays and vacuum tubes..
By today's standards, the machine was slow. In fact, it was only about a hundred times faster than a human operator using a desktop calculator..
- Predictor Kerrison.
- Librascope, aircraft weight and balance computer.
- Mechanical integrators such as the planimeter.
- Nomogram.
- Norden Bombardment Visor.
- Computers related to fire control.
- Water integrators.
- MONIAC, economic modeling.
The Simulation Council was an association of analog computer users in the United States.
The Simulation Council bulletins from 1952 to 1963 are currently available online. They show the technologies at that time and also the common use of analog computers.
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