What Does a Speed Sensor Do?
It is important to know how fast a vehicle is going for many reasons. Since speed effects handing and braking times, you can't make proper driving decisions if you do not know how fast you are going. Speed sensors measure how fast a vehicle is going.
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Location
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Speed sensors are typically located on a wheel hub or on an axle. The sensor counts the number of revolutions the wheel makes per minute to determine wheel speed. Depending on the car and its features, there may be more than one speed sensor on a car.
Basic Function
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The most basic use of a speed sensor is to provide information about speed to the speedometer. This information is also used by the cruise control system and to measure engine revolutions per minute (rpm). Only one sensor is needed for this type of information.
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ABS
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Many anti-lock brakes systems (ABS) require a sensor on each wheel to identify lockup and to adjust the timing of the brakes. Each wheel may be going at a different speed, so timing may need to be adjusted for each wheel.
Traction Control
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Traction control systems need data from each wheel to identify and stop individual wheel slip and to transfer power to the wheels that have more traction.
Electronic Stability Control
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Electronic stability control, which is mandated to be standard on all cars sold in the United States in 2012, uses data from the speed sensors on each wheel to correct for oversteer and understeer by using brakes and throttle to slow down certain wheels and speed up others.
Other Systems
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Some more sophisticated cars use speed sensors to judge when to lower the ride height of the vehicle and to tighten steering during higher speeds for better control.
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References
- Photo Credit red sport hatchback car racing drive high speed image by alma_sacra from Fotolia.com
