Analog Computer

Today, it is very rare to use or even see an analog computer in real life. But back in 1968, this was the type of computer that I first used while a Mechanical Engineering student at Michigan Technological University. I don’t remember what class it was for or the problem that I solved on it. I don’t remember what the exact model was either, but it was similar to a Donner Scientific 3100 shown at the Analog Computer Museum web site. I remember using a Problem Board on which we setup our solution and then plugged that into a bigger system.

Today’s digital computers are sequential devices, operating on data one step at a time. It represents data internally in a representation called binary. Thus a single transistor in a digital computer can only store two states, on and off, and requires many transistors to store a number to any degree of precision. Digital computers are programmed through instructions which switch transistors on and off at the lowest level.

An analog computer operates differently than the digital computer. It offers continuous solutions to the problems on which they are operating. All components of an analog computer are part of a complete circuit that operates in parallel. The system is setup with electrical components that simulate portions of a real system. A mechanical spring-mass system may be represented by resistors, capacitors and inductors. When a switch is thrown, the system starts operation and results are measured as voltages and currents.

Note that there were actually mechanical analog computers many centuries earlier. An automobile speedometer is a mechanical analog computer that measures the rotations per minute of the drive shaft and translates that measurement into a display of miles or kilometers per hour.