Analog computers sound almost ancient nowadays – but you‘ve likely used one quite recently! Those old-fashioned thermometers, speedometers, and mechanical watches? All simple types of analog computing devices.
According to computer engineering experts, an analog computer is:
"A device that processes continuously variable physical quantities like voltages to represent information and perform calculations, rather than a digital system based on discrete binary digits."
In other words, analog computers exploit properties like electricity, magnetism, and mechanics to model problems, rather than using codes and programming rules like modern digital computers do.
A Brief History of Analog Computers
The first known analogy computation devices emerged as early as the late 1800s. Serbian mathematician Mihajlo Petrovic Alas built one of the first hydraulic analog computers in the 1890s to model water flow.
Over the next few decades, engineers across Europe and America developed various mechanical calculation machines using gears, levers, and springs. However, these were mainly just experimental prototypes.
It wasn‘t until the 1930-40s that the field really took off, thanks to pioneers like:
- Albert A. Michelson – Built electrical analog computers using motors to solve differential equations
- Vannevar Bush – Developed the differential analyzer, one of the first advanced general-purpose analog computers
Key Analog Computer Milestones
| Year | Event |
|---|---|
| 1876 | James Thomson coins the term "analog" for continuous computation |
| 1931 | Vannevar Bush builds the differential analyzer, a breakthrough mechanical analog computer |
| 1941 | The M9 gun director, an early fire-control analog computer is deployed on US Navy ships in WW2 |
| 1960s | Analog computers are in widespread industrial and military use for simulations and controls |
| 1970s | Digital computers surpass and replace analog models for most applications |
During and after WW2, specialized analog computing devices were built for aiming weapons, encrypting communications, and even early flight simulations. However, by the 1960s-70s, digital computers offered far greater speed, precision and flexibility – relegating analog models niche roles.
How Do Analog Computers Actually Work?
Rather than using discrete digits like 0s and 1s, analog computers rely on measured, continuously varying physical quantities like:
- Voltage
- Fluid pressure
- Rotational speed
- Temperature
These signals act as analog representations of whatever parameter they‘re set to model.
For example, a voltage level can simulate velocity, with 0 volts representing 0 mph, 5 volts indicating 50 mph etc. Or a rotating shaft speed could act as a clock timer, with a faster rotation simulating the passage of more time.
Using various electrical, mechanical and hydraulic modules, these analog signals can then be manipulated using mathematical operations like addition, multiplication, integration etc. Just like software algorithms in a digital computer.
However, since analog signals fluidly vary like waves rather than jumping between discrete values, analog computers can more readily simulate the natural continuity of phenomena in the real physical world. This made them uniquely useful for applications like flight simulation, weapon aiming, radar signal processing and research lab experiments before the flexibility of software-driven digital devices took over.
Why Do We Still Use Some Analog Computers Today?
Given how astonishingly powerful even small digital devices have become, you might wonder why any analog computers still exist today.
Well, for some niche applications, analog computing methods still have advantages:
Simplicity – Mechanical analog devices require no programming, battery power or digital logic. This makes them sturdy and easy to use in rough environments.
Cost – Replacing dashboard speedometers in cars with digital velocity sensors would provide little benefit for a much higher price tag. Analog devices are sufficiently accurate for many everyday measurement purposes.
Physical Realism – Advanced physics and aerodynamics simulations sometimes couple digital computation with specialized analog feedback for more realistic experimental data. The continuous nuance of analog signals mimics natural systems better.
So while digital computers now dominate nearly every advanced computing application, from mobile phones to aircraft autopilots, analog techniques still fill some practical roles where they remain the simplest and most cost-effective solution. However, these analog devices are now very specialized, quite unlike pioneering early machines that first revealed the wonder of automatic computation and simulation many decades ago.
