For centuries speed sensors have been used to determine the speed of moving objects. In fact, the very first primitive speed sensors were lengths of rope with a knots tied in them that were tossed over the sides of moving ships to determine how many “knots” the ship was traveling at. However; the advent of the motorized wheeled carriage created the need for a more advanced mechanical speed sensor, such as the type that used a gear and a cable to run a speedometer on an automobile.
A Technological Need
As time and technology progressed however, the need for other types of accurate speed sensors developed. This in turn led to the development of what is often referred to as the magnetic speed sensor. So how do they work? How can a magnet detect and transmit the speed of a moving object?
The Hall Effect
It is not just the magnet in a magnetic speed sensor that is used to determine speed but an electrical current that surrounds the magnet as well. There is a certain electrical phenomena called the “Hall effect” that is used to determine the speed of an object with a magnet.
An Electrical Current
In short, when an electrical current is ran near a magnet and the magnet detects ferrous metal such as iron or steel the electrical current is effected. This electrical effect can then be transmitted by wires to a speed gauge where it can be displayed.
Gear Toothed Magnetic Sensor
Often a gear is used in conjunction with a magnetic speed sensor. As the gear spins or turns, each spline or tooth in it will be detected by the magnet as it passes and a corresponding electrical pulse is sent out. The faster the gear spins the faster the electrical pulses the sensor sends and thus a speed reading is made.