Even driving the vehicle in reverse can do the trick. Most instrument clusters today are fully electronic, so the cable-driven odometer is no longer used. Instead, a sensor and an electronic circuit now do the job. The current norm is a magnetic pick-up placed in close proximity to a toothed wheel in the gearbox auto or manual that induces pulses of current. The signal is sent from the sensor to the ECU, which converts the pulses to an appropriate voltage to activate a stepper-motor for a mechanical odometer or a printed circuit board for a digital odometer.
Further development of dashboard instrumentation has paved the way for multiple driving-related displays, including fuel economy information. By using the odometer signals and extracting relevant engine measurements from the ECU, the on-board computer can easily and accurately calculate fuel consumption and send the output to the LCD display.
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Sign up. Main Menu Search driving. This advertisement has not loaded yet, but your article continues below. Metal craftsman creating a coupe that never existed. Where do you park your car keys? Preventing relay attacks. The Volkswagen Tiguan gets a facelift, smarter interior, and new R-Line packages. Thanks for signing up! Instead of a spinning cable transmitting the distance signal, the distance along with a lot of other data is transmitted over a single wire communications bus from the engine control unit ECU to the dashboard.
The car is like a local area network with many different devices connected to it. Here are some of the devices that may be connected to the computer network in a car:. Many vehicles use a standardized communication protocol, called SAE J, to enable all of the different electronics modules to communicate with each other. The engine control unit counts all of the pulses and keeps track of the overall distance traveled by the car. This means that if someone tries to " roll back " the odometer, the value stored in the ECU will disagree.
This value can be read using a diagnostic computer, which all car-dealership service departments have. Several times per second, the ECU sends out a packet of information consisting of a header and the data. The header is just a number that identifies the packet as a distance reading, and the data is a number corresponding to the distance traveled.
The instrument panel contains another computer that knows to look for this particular packet, and whenever it sees one it updates the odometer with the new value. In cars with digital odometers, the dashboard simply displays the new value. Cars with analog odometers have a small stepper motor that turns the dials on the odometer. For more information on odometers and other often-overlooked car parts, check out the links on the next page.
Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. How Odometers Work. By: Karim Nice. Odometers accurately count miles through a system of gears. Mechanical Odometers " ". The output of the last worm gear drives a shaft that turns the tenth-of-a-mile indicator.
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