Odometer

An instrument that measures and displays the distance traveled by a vehicle or other moving object. It may record total distance, trip distance, or both.

Wheel circumference: The distance around a wheel, equal to its diameter multiplied by pi. A wheel-driven odometer estimates distance from each wheel revolution and its circumference.
Distance: A measure of the spatial separation between two points or the length of a path traveled. An odometer reports accumulated path length rather than a vehicle's displacement.
Trip computer: An onboard vehicle system that displays information such as trip distance, fuel use, and travel time. Trip computers commonly provide resettable distance readings alongside the odometer.
Speedometer: An instrument that displays the instantaneous speed of a vehicle. A speedometer measures speed at a moment, whereas an odometer accumulates distance.
Hall-effect sensor: A sensor that detects magnetic fields through the Hall effect and converts changes into electrical signals. Electronic odometers can count pulses from magnetic sensors monitoring wheel or drivetrain rotation.
Angular velocity: The rate at which an object rotates around an axis, measured as angle per unit time. Wheel rotation provides the motion signal from which many odometers derive distance.
Vehicle maintenance: Inspection, servicing, and repair performed to keep a vehicle safe and functional. Service schedules often call for work at specified odometer readings.
GPS tracking: The use of satellite-based positioning to determine and record an object's location over time. GPS estimates distance from position changes rather than counting wheel rotations.
Vehicle speed sensor: A device that measures a vehicle's speed, usually from rotating drivetrain or wheel components. Its rotation pulses can be accumulated over time to calculate distance.
Calibration: The process of adjusting or checking an instrument against a known measurement standard. Odometer accuracy depends on matching rotation counts to a vehicle's actual travel.

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