A hubometer (hub, center of a wheel + -ometer, measure of), or hubodometer or simply hubo, is a device mounted on the axle of an automobile or other vehicle that measures distance traveled.
The whole device rotates with the wheel except for an eccentrically mounted weight on an internal shaft. This remains pointing downwards and drives the counting mechanism as the body of the hubometer rotates round it.
They are needed on semi-trailers where they are the only means of measuring distance traveled over the lifetime of the trailer.
They are used on bus wheels where the tires are supplied to the bus operator by an independent company on a contract of "price per thousand kilometers". The hubometer is installed by the tire company to give them their own measure.
One of the first hubodometers was designed by Engler in 1952 patent number 2,638,374, which was later bought by Stemco and sold under the brand of Stemco Engler Hubodometers finally ending with the Stemco Hubodometer in the early 80's. Numerous attempts at electronic versions have been attempted including a stemco version patented in 1991 (pat #4,989,222), however; The first hubodometer with no moving parts was made by Stemco and released in 2002 under the name DataTrac, patent number 6,940,940 granted in 2005. This part was then made programmable in 2006. In 2005 the first solid state hubodometer was made into a backscatter RF device later being converted to an active RF mileage data collection device in 2007 and named the Active TracBat hubodometer. This newest version can be read by satellite asset tracking systems or gate reader systems as well as with handheld readers. It also still included the visual display that had been used on the datatrac device. In October of 2010 the third Generation of electronic hubodometers began shipping which included updates to the display and programming sequences and now can be used in off road applications with very high vibrations and intantaneous accelerations. (pat app #2011/0066397) The new model now supports calibrations of 1 to 1999 revs per count/mile/km. The RF enabled TracBat line was also upgraded to include the new improvements. The display now stays on at low speeds so that the counting operations can be viewed in realtime. Reprogrammability for the first few miles was also supported.