A crank sensor is a component used in an engine (or occasionally on a bicycle) to monitor crank position and/or rotational speed. Crank position does not usually need to be known accurately at all times, but engine management systems use a crank sensor to provide a datum as well as to provide a pulse from which engine speed can be calculated. An engine is something that produces some effect from a given input. ... This racing bicycle is built using lightweight, shaped aluminium tubing and carbon fiber stays and forks. ... An electronic control unit (ECU) (also known as an engine management system) is an electronic device, basically a computer, in an internal combustion engine that reads several sensors in the engine and uses the information to control the fuel injection and ignition systems of the engine. ...

Crank sensors in engines are usually based on the hall effect. Hall effect diagram, showing electron flow (rather than conventional current). ...