Editing Differential analyser (section)

{{Short description|Mechanical analogue computer to solve differential equations}}
{{about|analogue differential analysers|the digital implementation|Digital Differential Analyzer}}

[[Image:Harmonic analyser disc and sphere.jpg|thumb|right|[[Ball-and-disk integrator|Ball-and-disc integrator]] for studying [[Tide#Analysis|tides]].]]
The '''differential analyser''' is a mechanical [[analog computer|analogue computer]] designed to solve [[differential equation]]s by [[integral|integration]], using wheel-and-disc mechanisms to perform the integration.<ref>{{cite web|last=Irwin|first=William|url=http://amg.nzfmm.co.nz/differential_analyser_explained.html|title=The Differential Analyser Explained|access-date=2010-07-21|publisher=Auckland Meccano Guild|date=July 2009|archive-date=2018-11-24|archive-url=https://web.archive.org/web/20181124174422/http://amg.nzfmm.co.nz/differential_analyser_explained.html|url-status=bot: unknown}} Archived</ref> It was one of the first advanced computing devices to be used operationally.<ref>{{Cite encyclopedia
  | title = Invention of the modern computer
  | encyclopedia = [[Encyclopædia Britannica]]
  | publisher = www.britannica.com
  | url = http://www.britannica.com/EBchecked/topic/130429/computer/216032/Invention-of-the-modern-computer
  | access-date = 2010-07-26}}</ref>
In addition to the integrator devices, the machine used an epicyclic differential mechanism  to perform addition or subtraction - similar to that used on a front-wheel drive car, where the speed of the two output shafts (driving the wheels) may differ but the speeds add up to the speed of the input shaft. Multiplication/division by integer values was achieved by simple gear ratios; multiplication by fractional values was achieved by means of a multiplier table, where a human operator would have to keep a stylus tracking the slope of a bar. A variant of this human-operated table was used to implement other functions such as polynomials.