Speed Sensor

The numbers 40 and 75 correspond to the range of speed limits implemented in our country at present. Now how you will be able to know if the vehicle you’re driving is approaching these speed limits? The cruise control system maintains the driver’s desired set speed, by actuating the throttle-accelerator pedal linkage. Though it’s the cruise control system does that job, the wits that normally control the speed of the car is coming from the driver. The driver senses the speed by looking at the speedometer and then adjusting the pressure on the gas pedal or the brakes to compensate for variation in the desired speed.

But do you know where the speedometer gets the reading? It comes from the speed sensor. The vehicle’s speed sensor which is mounted on the output shaft of the transmission (some later models with mechanical speedometers have the speed sensor mounted behind the speedometer) sends electrical pulses to the computer, pulses which are generated through a magnet that spin a sensor coil. When the vehicle’s speed increases the frequency of the pulses also increases. Note that for any given speed of the vehicle, there is a corresponding pulse frequency. It is this pulse frequency which the cruise control tries to maintain as a constant. Speed sensors are usually made up of a toothed metal disk mounted on a rotating shaft and a stationary detector covering a magnetic coil.

There are various types of speed sensors used in every vehicle. There are cars which are equipped with two speed sensors that work for two different systems. The first is the engine speed sensor. Engine speed sensor is usually located on the vehicle’s crankshaft and is actually where the speedometer gets its data. The other type of speed sensor is the wheel speed sensor. This kind of speed sensor picks up impulses from the wheels and sends data to the anti-lock braking system or ABS. This data is then used by the system to foresee a condition when the wheels would lock up.

If the vehicle speed sensor fails, the cruise control system will not get a speed signal. If this is the case, most probably, the speedometer will usually stop working as well. So, before this thing occur, it is better to have a regular safeguarding on your speed sensors. Actually, maintaining the speed sensor is very easy. All you have to do is to remove the sensor and unscrew it from the case. Clean off all the iron particles carefully and there you go. However, if the speed sensor is chewed up in any way, replacing it is really necessary.