This document discusses speed sensors, including their construction, working, types, applications, advantages, and disadvantages. It describes how speed sensors typically consist of a ferromagnetic toothed wheel and sensor that measures the magnetic rotation speed to provide a voltage corresponding to rotation speed. Common types are magnetic, optical, and Hall effect sensors. Speed sensors are widely used in automotive and engineering applications to measure wheel, transmission, and other rotational speeds. Their advantages include being passive and inexpensive, while disadvantages include limitations for low speeds and additional circuitry needs.

1. SPEED SENSOR

2. CONTENTS:
INTRODUCTION
 SPEED SENSOR CONSTRUCTION
WORKING OF SPEED SENSOR
 TYPES OF SPEED SENSOR
 APPLICATIONS
 ADVANTAGES
 DISADVANTAGES

3. INTRODUCTION:
The speed sensor, an essential component for the
operation of several on-board systems, allows the
magnetic rotation speed to be measured in
order to provide a voltage corresponding to
the rotation speed. It is widely used in the
aeronautics, automotive and precision engineering
sectors.

4. SPEED SENSOR CONSTRUCTION:
• The most common wheel speed sensor system
consists of a ferromagnetic toothed reluctor ring
(tone wheel) and a sensor (which can be passive or
active).
• The tone wheel is typically made of steel and may be
an open-air design, or sealed. The number of teeth
is chosen as a trade-off between low-speed
sensing/accuracy and high-speed sensing/cost.
Greater numbers of teeth will require more
machining operations and produce a higher
frequency output signal which may not be as easily
interpreted at the receiving end, but give a better
resolution and higher signal update rate. In more
advanced systems, the teeth can be asymmetrically
shaped to allow the sensor to distinguish between
forward and reverse rotation of the wheel.

5. • A passive sensor typically consists of a
ferromagnetic rod which is oriented to project
radially from the tone wheel with a permanent
magnet at the opposite end. The rod is wound with
fine wire which experiences an induced alternating
voltage as the tone wheel rotates, as the teeth
interfere with the magnetic field. Passive sensors
output a sinusoidal signal which grows in
magnitude and frequency with wheel speed.
• A variation of the passive sensor does not have a
magnet backing it, but rather a tone wheel which
consists of alternating magnetic poles produce the
alternating voltage. The output of this sensor tends
to resemble a square wave, rather than a sinusoid,
but still increases in magnitude as wheels speed
increases.

6. WORKING OF SPEED SENSOR:
• How does the speed sensor work? The vehicle speed sensor
measures the rotational speed of the gears in your
transmission system. Then, it converts this measurement
into an analog signal or a low voltage square wave signal and
relays it to electronic control units (ECUs) inside your car

7. TYPES OF SPEED SENSOR:
Magnetic speed sensors.
Optical speed sensors.
Hall effect speed sensors.
Gear tooth sensor.
Transmission speed sensors.
Wheel speed sensors.
ABS wheel speed sensors.
Angular speed sensors

8. APPLICATIONS:
• The speed sensor, an essential component for the operation of
several on-board systems, allows the magnetic rotation speed to
be measured in order to provide a voltage corresponding to the
rotation speed. It is widely used in the aeronautics,
automotive and precision engineering sectors.

9. ADVANTAGES:
• Variable reluctance sensors are passive sensors as they don’t
require external power supply
• As the wire and magnets used are pretty inexpensive, these
sensors are low cost sensors
• They are light weight, robust and can work in harsh(high
temperature and high vibration) environments

10. DISADVANTAGES:
• Target material must be ferrous only.
• As the magnitude of the induced voltage in these sensors is
proportional to target speed, it becomes difficult to design
circuitry appropriate for very low speed signals. Thus Variable
Reluctance sensors have a definite lower limit on the speed of
the target.
• Though sensors themselves are cheap, the cost advantage is
offset by the additional electronic circuitry required to process
the low amplitude induced voltages.

11. THANK YOU