Ball-and-disk integrator

Typical uses were the measurement of area or volume of material in industrial settings, range-keeping systems on ships, and tachometric bombsights.

The first input is a spinning disk, generally electrically driven, and using some sort of governor to ensure that it turns at a fixed rate.

As the water level rises, the bearing is pushed farther from the center of the input disk, increasing the output's rotation rate.

The output was then fed into a similar machine, the Harmonic Synthesiser, which spun several wheels to represent the phase of the contribution from the sun and moon.

[2] A number of similar systems followed, notably those of Leonardo Torres Quevedo, a Spanish physicist who built several machines for solving real and complex roots of polynomials;[3] and Michelson and Stratton, whose Harmonic Analyser performed Fourier analysis, but using an array of 80 springs rather than Kelvin integrators.

Additionally, the gunners could no longer directly spot the fall of their own shot, relying on the spotters to do this and relay this information to them.

The solution was the Dreyer table, which used a large ball-and-disk integrator as a way to compare the motion of the target relative to the ship, and thereby calculate its range and speed.

The US Navy used a somewhat simpler device known as the Rangekeeper, but this also saw continual modification over time and eventually turned into a system of equal or greater sophistication to the UK versions.

By comparing the calculated output with the actual motion of objects on the ground, any difference would be due to the effects of wind on the aircraft.

Dials setting these values were used to zero out any visible drift, which resulted in accurate wind measurements, formerly a very difficult problem.

Ball disk integrators were used in the analog guidance computers of ballistic missile weapon systems as late as the mid 1970s.