Magnetic Sensors

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 gage 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.

Watch the video related to magnetic sensors

Behind the scenes of Discovery Channel’s Prototype This from the Virtual Sea Adventure episode. Final test of the control system for our underwater ROV controller. Control is achieved by using two Melexis MLX90333 3-D Joystick Position Sensors. The user, under water, wears gloves with magnets embedded in the thumbs and moves his thumbs over the sensors to control the various aspects of the ROV. The analog outputs of the sensor’s X- and Y-axis are fed through an A/D, into a BASIC Stamp …

Help answer the question about magnetic sensors

how do i glue a magnetic alarm sensor to my door?
i have a wireless alarm system. the little magnetic sensor on my slider won't stay glued to the metal door because it keeps getting pulled off by a screw in the frame. i have used crazy glue, gorilla glue, tape, and some gummy adhesive stuff to no avail. i can't use my alarm unless the sensor is in place. any ideas???

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Written by Rosa Telipten. Now you can learn all you wanted to know about Magnetic Speed Sensors and you will even find articles on Variable Reluctance Pickup

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