UNIT II - MOTION, PROXIMITY AND RANGING SENSORS

MR3491 SENSORS AND INSTRUMENTATION
UNIT II - MOTION, PROXIMITY AND
RANGING SENSORS
Prepared by
A.R.SIVANESH
Assistant Professor
Department of Mechanical Engineering
Sri Ranganathar Institute of Engineering and Technology,
Coimbatore
1
Prepared by Sivanesh A R, AP/MECH

SYLLABUS
Motion Sensors – Potentiometers, Resolver,
Encoders – Optical, Magnetic, Inductive,
Capacitive,LVDT – RVDT – Synchro – Microsyn,
Accelerometer – GPS, Bluetooth, Range Sensors –
RF beacons, Ultrasonic Ranging, Reflective
beacons, Laser Range Sensor (LIDAR).
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7

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24

25

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POTENTIOMETER SENSOR
27

POTENTIOMETER SENSOR
A POTENTIOMETER CONSIST OF A RESISTANCE ELEMENT WITHA SLIDING
CONTACT WHICH CAN BE MOVED ALONG THE LENGTH OF THE ELEMENT .
SUCH ELEMENT CAN BE USED FOR LINEAR OR ROTARY DISPLACEMENTS,
THE DISPLACEMENT BEING CONVERTED INTO A POTENTIALDIFFERENCE
28

THE ROTARY POTENTIOMETER CONSIST OF CIRCLE WIRE WOUND TRRACK OR A FLIM
OF CONDUCTIVITY PLASTIC WHICH IS ROTATABLESLIDING CONTACT CAN BE ROTATED
29

• It works on the principle of conversion of
mechanical displacement into an electrical
signal.
• The sensor has a resistive element and a
sliding contact (wiper). The slider moves along
this conductive body, acting as a movable
electric contact.
30

• The output voltage is
proportional to the
displacement of the
slider over the wire
• Then the output
parameter
displacement is
calibrated against the
output voltage VA.
31

APPLICATION
machine-tool controls
Elevators
automobile throttle controls
control of injection molding machines
woodworking machinery
Printing
Spraying
robotics
32

Resolver
33

What is a Resolver?
 A resolver is an electromagnetic transducer that can be used in a wide
variety of position and velocity feedback applications which includes light
duty/servo, light industrial or heavy duty applications. Resolvers, known as
motor resolvers, are commonly used in servo motor feedback applications
due to their good performance in high temperature environments.
 Because the resolver is an analog device and the electrical outputs are
continuous through one complete mechanical revolution, the theoretical
resolution of a single speed resolver is infinite. Because of its simple
transformer design and lack of any on board electronics, the resolver is a
much more rugged device than most any other feedback device and is the
best choice for those applications where reliable performance is required in
those high temperature, high shock and vibration, radiation and
contamination environments which makes the resolver the sensible design
alternative for shaft angle encoding.
34

Resolver Design
 The resolver is a special type of rotary transformer that consists of a
cylindrical rotor and stator. Both the rotor and the stator are
manufactured with multi-slot laminations and two sets of windings. The
windings are normally designed and distributed in the slotted
lamination with either a constant pitch-variable turn or variable pitch-
variable turn pattern. In either case, the winding distribution is in a
sinusoidal pattern.
 The windings for a single speed resolver create one complete Sine curve
and Cosine curve in one mechanical revolution while the windings for a
multi-speed resolver create multiple Sine and Cosine curves in one
mechanical revolution. While a single speed provides absolute feedback
and the multi-speed does not, the multi-speed does provide better
accuracy.
35

 The number of speeds available is limited by the size of the
resolver. The two sets of windings are positioned in the
laminations at 90 degrees to each other. These are called
the Sine and Cosine windings. One set of windings in the
rotor are normally shorted internally to improve the
accuracy.
36

How Does a Resolver Work?
 A resolver outputs signal by energizing the input phase of the resolver with
an AC voltage (VAC) to induce voltage into each of the output windings. The
resolver amplitude modulates the VAC input in proportion to the Sine and
the Cosine of the angle of mechanical rotation. The resolver is sometimes
known as an Analog Trigonometric Function Generator or a Control
Transmitter. The function of the resolver is to resolve a vector into its
components (Sine and Cosine). Electrical Zero (EZ) is defined as the position
of the rotor with respect to the stator at which there is minimum voltage
amplitude across the Sine winding and the maximum voltage amplitude
across the Cosine winding when the input winding is excited with the rated
voltage.
 The rotor position or angle is simply the Arc tan of the voltage output of the
Sine winding divided by the output of the Cosine winding. This ratio metric
format provides an inherent noise reduction feature for any injected noise
whose magnitude is approximately equivalent on both windings and also
results in a large degree of temperature compensation.
37

There are 7 functional operating parameters
which define the resolver operation. These are:
 Accuracy
 Input Excitation Voltage
 Input Excitation Frequency
 Input Current Maximum
 Transformation Ratio of Output Voltage to the Input
Voltage
 Phase shift of the Output Voltage from the Input Voltage
 Null Voltage
38

Resolver Applications
 Servo motor feedback
 Speed and position feedback in steel and paper mills
 Oil and gas production
 Jet engine fuel systems
 Aircraft flight surface actuators
 Communication position systems
 Control systems in land based military vehicles
39

Encoders
40

Encoders
 An encoder is a sensing device that provides feedback.
Encoders convert motion to an electrical signal that can be
read by some type of control device in a motion control
system, such as a counter or PLC. The encoder sends a
feedback signal that can be used to determine position,
count, speed, or direction.
 An encoder detects the rotation of objects as a physical
change amount by the sensor element, and finally transmits
rotation/angle information to the outside as an electrical
signal. An encoder is classified into four types: mechanical,
optical, magnetic, and electromagnetic induction types.
41

Optical Encoders
• Any transducer that generates a coded reading
of a measurement can be termed anencoder.
• Shaft Encodersare digital transducers that
are used for measuring angular
displacements and velocities.
• Relative advantages of digital transducers
over their analog counterparts:
– High resolution (depending on the word size of the
encoder output and the number of pulses per
revolution of the encoder)
– High accuracy (particularly due to noise immunity
of digital signals and superior construction)
42

– Relative ease of adaptation in digital control
systems (because transducer output is digital) with
associated reduction in system cost and
improvement of system reliability
• Shaft Encoders can be classified into two
categories depending on the nature and method of
interpretation of the output:
– Incremental Encoders
– Absolute Encoders
• Incremental Encoders
– Output is a pulse signal that is generated when the
transducer disk rotates as a result of the motion that is
being measured.
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–By counting pulses or by timing the pulse width using a
clock signal, both angular displacement and angular
velocity can be determined.
– Displacement, however, is obtained with respect to
some reference point on the disk, as indicated by a
reference pulse (index pulse) generated at that location
on the disk. The index pulse count determines the
number of full revolutions.
• Absolute Encoders
– An absolute encoder has many pulse tracks on its
transducer disk.
– When the disk of an absolute encoder rotates, several
pulse trains – equal in number to the tracks on the disk
– are generated simultaneously.
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– At a given instant, the magnitude of each pulse signal
will have one of two signal levels (i.e., a binary state)
as determined by a level detector. This signal level
corresponds to a binary digit (0 or 1). Hence, the set of
pulse trains gives an encoded binary number at any
instant.
– The pulse windows on the tracks can be organized into
some pattern (code) so that each of these binary
numbers corresponds to the angular position of the
encoder disk at the time when the particular binary
number is detected.
– Pulse voltage can be made compatible with some form
of digital logic (e.g., TTL)
– Direct digital readout of an angular position is possible.
45

– Absolute encoders are commonly used to
measure fractions of a revolution. However,
complete revolutions can be measured using
an additional track that generates an index
pulse, as in the case of an incremental
encoder.
• Signal Generation can be accomplished using any
one of four techniques:
– Optical (photosensor) method
– Sliding contact (electrical conducting) method
– Magnetic saturation (reluctance) method
– Proximity sensor method
• Method of signal interpretation and processing is
the same for all four types of signal generation.
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(slits)
Schematic Representation of an Optical Encoder
One Track and One Pick-Off Sensor Shown
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In Binary Code, bit
switching may not
take place
simultaneously.
Schematic Diagram of an
Absolute Encoder Disk
Pattern
(a) Binary code
(b) Gray code
Ambiguities in bit switching can be
avoided by using gray code.
However, additional logic is needed
to covert the gray-coded number to a
corresponding binary number.
Absolute
Encoders must be
powered and
monitored only
when a reading is
taken. Also, if a
reading is missed,
it will not affect
the next reading.
48

(Electrically Insulating Material)
Schematic Representation of a Sliding Contact Encoder
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Pulse peak: nonmagnetic are Pulse valley: magnetic area
Schematic Representation of a Magnetic Encoder
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• Elements of the Optical Encoder
– The optical encoder uses an opaque disk (code disk)
that has one or more circular tracks, with some
arrangement of identical transparent windows (slits)
in each track.
– A parallel beam of light (e.g., from a set of light-
emitting diodes) is projected to all tracks from one
side of the disk.
– The transmitted light is picked off using a bank of
photosensors on the other side of the disk that
typically has one sensor for each track.
– The light sensor could be a silicon photodiode,
a phototransistor, or a photovoltaic cell.
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– Since the light from the source is interrupted by the
opaque areas of the track, the output signal from the
probe is a series of voltage pulses. This signal can be
interpreted to obtain the angular position and angular
velocity of the disk.
– Note that an incremental encoder disk requires only one
primary track that has equally spaced and identical
window (pick-off) areas. The window area is equal to
the area of the inter-window gap. Usually, a reference
track that has just one window is also present in order
to generate a pulse (known as the index pulse) to
initiate pulse counting for angular position
measurement and to detect complete revolutions.
52

– In contrast, absolute encoder disks have several rows of
tracks, equal in number to the bit size of the output data
word. Furthermore, the track windows are not equally
spaced but are arranged in a specific pattern on each
track so as to obtain a binary code (or gray code) for the
output data from the transducer.
– It follows that absolute encoders need as least as many
signal pick-offsensors as there are tracks, whereas
incremental encoders need one pick-off sensor to detect
the magnitude of rotation and an additional sensor at a
quarter-pitch separation (pitch = center-to-center
distance between adjacent windows) to identify the
direction of rotation, i.e., theoffset sensor
configuration.
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–Some designs of incremental encoders have two
identical tracks, one a quarter-pitch offset from the
other, and the two pick-off sensors are placed radially
without any circumferential offset, i.e., theoffset track
configuration.
– A pick-off sensor for a reference pulse is also used.
• Signal interpretation depends on whether the
particular optical encoder is an incremental device
or an absolute device.
– We will focus on the incremental optical encoder.
– The output signals from either the offset sensor
configuration or the offset track configuration are the
same.
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– Note that the pulse width and pulse-to-pulse period
(encoder cycle) are constant in each sensor output when
the disk rotates at constant angular velocity. When the
disk accelerates, the pulse width decreases
continuously; when the disk decelerates, the pulse
width increases continuously.
– The quarter-pitch offset in sensor location or track
position is used to determine the direction of rotation of
the disk. It is obtained by determining the phase
difference of the two output signals, using phase-
detection circuitry. One method for determining the
phase difference is to time the pulses using a high-
frequency clock signal.
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Incremental Optical Encoder Disk
Offset-Sensor Configuration
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Incremental Encoder Pulse Signals
(a) CW rotation (b) CCW rotation (c) reference
Clockwise (CW)
rotation:
V1 lags V2 by a quarter of a cycle
(i.e., a phase lag of 90°)
Counterclockwise (CCW) rotation:
V1 leads V2 by a quarter of a cycle
57

• Two methods are available for determining
velocities using an incremental encoder:
– pulse-counting method
– pulse-timing method
• Pulse-Counting Method
– The pulse count over the sampling period of the digital
processor is measured and is used to calculate the
angular velocity. For a given sampling period, there is
a lower speed limit below which this method is not very
accurate.
58

– To compute the angular velocityω, suppose that the count during a
sample period T is n pulses. Hence, the average time for one
pulse is T/n. If there areN windows on the disk, the average time for
one revolution is NT/n. Hence ω (rad/s) = 2π n/NT.
• Pulse-Timing Method
– The time for one encoder cycle is measured using a high-frequency
clock signal. This method is particularly suitable for measuring low
speeds accurately.
– Suppose that the clock frequency is f Hz. If m cycles of the clock signal
are counted during an encoder period (interval between two adjacent
windows), the time for that encoder cycle (i.e., the time to rotate
through one encoder pitch) is given by m/f.
– With a total of N windows on the track, the average time for one
revolution of the disk is Nm/f. Hence ω = 2πf/Nm.
59

Magnetic encoder
60

Magnetic encoder
 The magnetic encoder detects rotational position information
as changes of the magnetic field, converts them into electrical
signals, and outputs them. The simplest magnetic encoder
consists of a permanent magnet and a magnetic sensor. The
permanent magnet is attached to the tip of a rotating body
such as a motor shaft, and the magnetic sensor is fixed in a
state where it is mounted on a PCB board at a position where it
receives the magnetic field generated by the permanent
magnet. When the permanent magnet attached to the motor
shaft rotates, the direction of the magnetic field detected by
the magnetic sensor changes, as a result the encoder detects
the rotational position and speed of the motor shaft.
61

Magnetic encoder
 In the following, details about the principle of operation
until the change of the magnetic field distribution is
converted into angular information, using a magnetic
encoder consisting of a magnetic sensor called a Hall
element and a permanent magnet. The Hall element is a
magnetic sensor that uses the phenomenon of the Hall
effect to output a voltage proportional to the strength of
the magnetic field.
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Magnetic encoder
63

Principle of magnetic encoder
 When the motor shaft rotates, the magnetic field created by
the permanent magnet attached to the tip of the shaft also
rotates. At this time, the magnetic field rotates with
constant strength in the area near the center of the rotation
axis. The Hall element detects this change of magnetic field
distribution and converts it into an electrical signal. The Hall
element is a magnetic sensor that can only detect the
strength of a magnetic field in a single direction. Therefore,
in order to detect the rotational position of the XY rotation
plane, a Hall element for detecting the strength of the X
axis component (Bx) and a Hall element for detecting the
strength of the Y axis component (By) are required.
64

Advantages and applications of
magnetic encoder
 Since the magnetic encoder has a mechanism to detect
changes of the magnetic field, it has an excellent advantage of
being robust in an environment contaminated with dust, oil,
water, etc. Therefore, it is suitable for use in environments with
a lot of dust, oil, and water. For example, magnetic encoders are
used in industrial sewing machines used in environments with a
lot of lint and machine tools used in environments where
cutting oil and water splash.
 Another advantage is that it is possible to manufacture an
encoder that outputs an absolute angle with a very simple
structure of a rotation angle sensor IC and a permanent
magnet. Therefore, it is suitable for applications that require
small size, light weight, and high reliability. For example, it is
used in machine tools that use small-diameter motors and
factory automation machines that require durability.
65

Inductive encoders
66

Inductive encoders
 Position measuring devices that rely on the principle of
mutual induction include resolvers, linear variable
differential transformers (LVDTs), and inductive encoders.
Two of these technologies — resolvers and LVDTs — are
based on the construction and operation of a transformer.
 In the case of an LVDT, voltage is applied to a primary
winding and induced in two secondary windings — located
on either side of the primary — via a ferromagnetic core.
Distance is determined by the differential voltage output by
the two secondary windings, and direction is determined by
whether the output voltage is in phase or out of phase with
the primary voltage.
67

Inductive encoders
68

Inductive encoders
 In the case of a resolver, a rotary transformer applies voltage to
the primary winding, which is located on the rotor. Voltage is
then induced in two secondary windings, oriented at 90
degrees as sine and cosine, on the stator. Position is
determined by the ratio of the voltages in the secondary
windings, and direction is determined by analyzing which
secondary voltage (sine or cosine) is leading.
 Inductive encoders are similar to LVDTs and resolvers, but
instead of using traditional windings, they use flat coils
(sometimes referred to as “traces”) manufactured onto printed
circuit boards. Rotary inductive encoders contain two main
parts — a stator (also referred to as the sensor) and a rotor
(also referred to as the target).
69

Inductive encoders
 The stator contains a transmitter coil and two (or sometimes
more) receiver coils, printed onto the circuit board – or in some
cases, directly onto the stator substrate. The receiver coils are
printed so that they produce sine and cosine waves. In many
designs, electronic circuitry for signal processing is also
integrated onto the stator. The rotor, or target, is passive and is
either made of ferromagnetic material or made of a substrate
containing layers, or patterns, of conductive material such as
copper.
 When voltage is applied to the transmitter coil on the stator, or
sensor, an electromagnetic field is produced. As the rotor, or
target, passes over the sensor, eddy currents are generated on
the surface of the target. These eddy currents generate an
opposing field, which reduces the flux density between the
sensor and the target, causing a voltage to be generated at the
receiver coils on the sensor. The amplitudes and phases of the
receiver voltages change as the target moves, and the position
of the target can be determined from these voltages.
70

Inductive encoders
 Inductive encoders are also available in linear versions. Here,
the target is a linear scale with ferromagnetic (or electrically
conducting) gratings, or stripes. The sensor (also referred to as
the read head) contains the transmitter and receiver coils as
well as electronics for signal processing. As the read head
travels along the scale, the gratings of the scale cause
variations in the voltages induced in the receiver coils, and
these voltages indicate the sensor’s linear position.
 Inductive encoders provide absolute position information and
have accuracies that fall between that of magnetic and optical
technologies — without the strict mounting considerations of
optical encoders. And they’re insensitive to nearly all forms of
contamination or interference, including liquids, dirt and dust,
magnetic fields, EMI, and even severe vibrations. For rotary
measuring applications, the printed circuit board construction
of inductive encoders gives them a much smaller form factor
and more design flexibility than their resolver counterparts.
71

Capacitive encoders
 Two types of encoders dominate the general industrial
market—optical and magnetic. But capacitive encoders, a
relatively new introduction, offer resolution comparable to
optical devices, with the ruggedness of magnetic encoders.
Currently, there are only a handful of vendors for capacitive
encoders, but their suitability for applications requiring high
precision and durability make them a good choice for the
semiconductor, electronics, medical, and defense industries.
72

How capacitive encoders work
 The basic principle behind capacitive encoders is that they
detect changes in capacitance using a high-frequency
reference signal. This is accomplished with the three main
parts—a stationary transmitter, a rotor, and a stationary
receiver. (Capacitive encoders can also be provided in a
“two-part” configuration, with a rotor and a combined
transmitter/receiver.) The rotor is etched with a sinusoidal
pattern, and as it rotates, this pattern modulates the high-
frequency signal of the transmitter in a predictable way.
 The receiver disk reads the modulations, and on-board
electronics — a proprietary ASIC is used by the vendor CUI
Inc. — translate them into increments of rotary motion. The
electronics also produce quadrature signals for incremental
encoding, with resolution ranging from 48 to 2,048 pulses
per revolution (PPR).
73

74

 Capacitive encoders work by transmitting a high-frequency
signal through a rotor that is etched with a sinusoidal pattern.
As the rotor moves, this pattern modulates the signal in a
predictable way. The receiver reads the modulations, and on-
board electronics translate them into increments of rotary
motion.
 In the proprietary capacitive Electric Encoder by Netzer
Precision Motion Sensors, the encoder has two operating
modes: Coarse Mode and Fine Mode. Coarse Mode is typically
used upon system start-up, to determine the initial position.
The encoder is then switched to Fine Mode for ongoing
operation. By breaking up the total measuring range into small,
equal, distinct segments, the scale of each segment can be
much finer than if the same scale were used over the entire
measuring range. This enables very high resolution without
added expense.
75

LVDT (LINEAR VARIABLE
DIFFERENTIAL TRANSFORMER)
76

LVDT (LINEAR VARIABLE DIFFERENTIAL TRANSFORMER)
DIFFERENTIAL TRANSFORMER
77

Cont.…
• Construction of LVDT:
78

LVDT
• CONSIST OF THREE COIL SYMMETERICALLY SPACED ALONG THE INSULATED
TUBES
• THE LEFT SIDE COIL IS PRIMARY COIL AND OTHER TWO COILS ARE
SECONFARY COIL WHICH ARE CONNECTED PARALLEL TO EACH OTHER.
• THE MAGNETIC OR IRON CORE MOVE BETWEEN THIS TWO COIL ASTHE
RESULT OF THE DISPLACEMENT BEING MONITORED
• THE AC INPUT TO THE PRIMARY COIL,AC EMF ARE INDUCED INTHE
SEECONDARY COIL
• As the core moves, these mutual inductances change, causing the voltages
induced in the secondary's to change. The coils are connected in reverse
series, so that the output voltage is the difference (hence "differential")
between the two secondary voltages. When the core is in its central
position, equidistant between the two secondary's, equal but opposite
voltages are induced in these two coils, so the output voltage is zero.
79

Linear variable differential transformer
(LVDT)
80

• Linear variable differential transformer (LVDT) is a
primary transducer used for measurement of linear
displacement with an input range of about ± 2 to ± 400
mm in general.
• It has three coils symmetrically spaced along an
insulated tube.
• The central coil is primary coil and the other two are
secondary coils.
• Secondary coils are connected in parallel in such a way
that their outputs oppose each other. A magnetic core
attached to the element of which displacement is to be
monitored is placed inside the insulated tube.
81

• Due to an alternating voltage input to the primary coil,
alternating electromagnetic forces (emfs) are
generated in secondary coils
• When the magnetic core is centrally placed with its
half portion in each of the secondary coil regions then
the resultant voltage is zero
• If the core is displaced from the central position as
shown in Figure 2.2.7, say, more in secondary coil 1
than in coil 2, then more emf is generated in one coil
• If the magnetic core is further displaced, then the
value of resultant voltage increases in proportion with
the displacement
82

Characteristics of LVDT:
83

The linear variable differential transformer (LVDT) is a type of electrical transformer used for
measuring linear displacement. The transformer has three solenoidal coils placed end-to-end
around a tube. The center coil is the primary, and the two outer coils are the secondaries. A
cylindrical ferromagnetic core, attached to the object whose position is to be measured, slides
along the axis of the tube.
An alternating current is driven through the primary, causing a voltage to be induced in each
secondary proportional to its mutual inductance with the primary. The frequency is usually in the
range 1 to 10 kHz.
As the core moves, these mutual inductances change, causing the voltages induced in the
secondaries to change. The coils are connected in reverse series, so that the output voltage is the
difference (hence "differential") between the two secondary voltages. When the core is in its
central position, equidistant between the two secondaries, equal but opposite voltages are
induced in these two coils, so the output voltage is zero.
When the core is displaced in one direction, the voltage in one coil increases as the other
decreases, causing the output voltage to increase from zero to a maximum. This voltage is in phase
with the primary voltage. When the core moves in the other direction, the output voltage also
increases from zero to a maximum, but its phase is opposite to that of the primary. The magnitude
of the output voltage is proportional to the distance moved by the core (up to its limit of travel),
which is why the device is described as "linear". The phase of the voltage indicates the direction of
the displacement.
Because the sliding core does not touch the inside of the tube, it can move without friction,
making the LVDT a highly reliable device. The absence of any sliding or rotating contacts allows the
LVDT to be completely sealed against the environment.
LVDTs are commonly used for position feedback in servomechanisms, and for automated
measurement in machine tools and many other industrial and scientific applications.
84

Rotary Variable Differential
Transformer (RVDT)
85

Transformer (RVDT)
 The transformer which senses the angular displacement of the conductor
is known as the Rotary Variable Differential Transformer or RVDT. It is the
type of electromechanical transducer which gives the linear output
proportional to the input angular displacement.
 The circuit of RVDT is shown in the figure below. The working of the
RVDT is similar to the LVDT. The only difference is that the LVDT uses the
soft iron core for measuring the displacement, whereas the RVDT uses
the cam shape core rotated between the primary and secondary winding
with the help of the shaft.
86

Transformer (RVDT)
87

Transformer (RVDT)
 The differential output voltage of the transformer increases
when the shaft rotates in a clockwise direction. And it
decreases when the shaft moves in an anti-clockwise
direction. The magnitude of the output voltage depends on
the angular displacement and the direction of the shaft.
 When the Core is at Null Position
 In the first condition, when the shaft is placed at the null
position then the induced e.m.f in the secondary windings
are similar although reverse in phase. Thus, the differential
o/p potential will be zero, and the condition will be E1 = E2,
where E0 = E1-E2 =0
88

Transformer (RVDT)
 When the Core Rotates in Clockwise Direction
The second condition, when the shaft rotates in the direction of
clockwise; more section of the core will enter across the primary
winding. Therefore, the induced e.m.f across the primary winding is
higher than secondary winding. Hence, the differential o/p
potential is positive, and the condition will be E1 > E2, where E0 =
E1-E2 = positive.
 When the Core Rotates in Anticlockwise Direction
In the third condition, when the shaft rotates in the direction of
anticlockwise, more section of the core will be entered across the
secondary winding. Thus, the induced e.m.f across the secondary
coil is higher than the primary coil. Hence, the differential o/p
potential is negative that means 1800 phase shift, and the
condition will be E1 < E2, where E0 = E1-E2 = negative.
89

RVDT Advantages
The advantages of RVDT include the following.
 The consistency of RVDT is high
 The exactness of RVDT is high
 The lifespan is long
 The performance is repeatable
 The construction is compact and strong
 Durability
 Low cost
 Easy to handle electronic components
 Resolution is infinite
 Linearity is Excellent
 A wide range of dimension ranges
90

RVDT Disadvantages
The disadvantages of RVDT mainly include the following
 The contact among the measuring exterior as well as the
nozzle is not possible for all time.
 The output of the RVDT is linear (about +40 or -40
degrees), so it restricts the usability.
91

RVDT Applications
The applications of RVDT include the following.
 Fuel Valves as well as Hydraulic
 Modern machine tools
 Controls Cockpit
 Controls Fuel
 Brake with cable systems
 Engines bleed air-systems
 Robotics
 Aircraft and Avionics
 Process Control industry
 Weapon and Torpedo Systems
 Engine fuel control
 Nose wheel steering systems
 Fly by wire systems
 Push reverser
 Actuators for controlling Flight as well as Engine
 Ecological control systems Prepared by Sivanesh A R, AP/MECH
92

SYNCHRO
93

SYNCHRO
 Synchros are electromagnetic devices that are used to
transmit positional data electrically from one location to
another. It can also be used to compute the sum of two
rotations, or the difference in angle between them and they
are also used in applications that require low output
torques. It can also be called as an electromagnetic
transducer which can convert the angular position of the
shaft into an electrical signal. Mostly AC transmission
system is known as synchros because of their synchronous
action in reproducing the angular movement of a shaft.
94

Principle operation of synchro
 Synchro is a form of a rotating transformer that resembles a small
AC motor and they are widely used as an element of measuring and
control systems involving rotatable shafts. The primary coil is
wound on the rotor and couples magnetically to the secondary
coils on the stator and the connections to the external terminals are
through slip rings. Synchros mostly have three secondary windings
arranged 120 degrees apart to give the varying voltage ratios as the
primary winding is rotated. The rotor energizing voltage is an AC
reference voltage at 50 Hz and this induces a voltage across each
stator winding which is dependent on the instantaneous angle
between the rotor and stator coil axes. So the voltage across any
pair of stator terminals is, therefore, the sum or difference,
depending on the phase of the individual stator winding voltages. It
can also be called as an electromechanical transducer. The
magnitude of the magnetic coupling varies between the primary
and secondary according to the position of the rotating element.
This, in turn, varies the magnitude of the output voltage
95

SYNCHRO
96

How synchro is used in servo
system
Control synchro system
 The control synchro system is the most common of all
synchros and is extensively used in aircraft and navigation
systems. Control synchros are similar to the torque synchros
but the signal from the receiver is going to be amplified to
drive output and the impedance of the windings is much
higher so there is no danger of the system burning out. The
control transformer can act as a null detector and can be
used in servo systems. Control synchros can be used in
electromechanical servo and shaft positioning.
97

What is the use of synchro
 It can be used for electromechanical servo and shaft
positioning and control synchros are used in aircraft
instruments and navigation systems. Synchros are used for
data transmission and it is used in radar antenna. Synchros
can be used in measurement and control applications
98

Microsyn
99

Microsyn
 This is a variable-reluctance transducer used to detect small
motions, giving output signals as low as 0.01° of changes in
angles.
 The figure below shows an example of Microsyn:
100

Microsyn
 In the Microsyn transducer above, the coils are connected in such a
way that at the null position of the rotary element, the voltages in
coils 1 and 3 are balanced by voltages induced in coils 2 and 4.
 The motion of the rotor in the clockwise direction increases the
reluctance of coils 1 and 3 while decreasing the reluctance of coils 2
and 4, thus giving a net output voltage vo.
 The movement in the counterclockwise direction causes a similar
effect in coils 2 and 4 with a 180° phase shift. A direction sensitive
output can be obtained by using phase-sensitive demodulators
 The sensitivity of the device can be made as high as 5 V per degree
of rotation. The nonlinearity may vary from 0.5% to 1.0% full scale.
 The key benefits of these transducers are that the rotor does not
have windings and slip-rings and the magnetic reaction torque is
also negligible.
101

Application
 Microsyn transducers are expansively used in applications
involving gyroscopes.
102

Accelerometer Sensor
103

Accelerometer Sensor
 The rate of change of velocity of the body with respect to
time is called acceleration. According to relative theory,
depending upon the relative object taken to measure
acceleration, there are two types of acceleration. The proper
acceleration, which is the physical acceleration of the body
relative to inertia or the observer who is at rest relative to
the object being measured.
 The coordinate acceleration depends upon the choice of
coordinate system and choice of observers. This is not
equal to proper acceleration. Accelerometer sensor is the
electromechanical device used to measure the proper
acceleration of the object.
104

Working Principle
 The basic underlying working principle of an accelerometer
is such as a dumped mass on a spring. When acceleration is
experienced by this device, the mass gets displaced till the
spring can easily move the mass, with the same rate equal
to the acceleration it sensed. Then this displacement value
is used to measure the give the acceleration.
 Accelerometers are available as digital devices and analog
devices. Accelerometers are designed using different
methods. Piezoelectric, piezoresistive and capacitive
components are generally used to convert the mechanical
motion caused in accelerometer into an electrical signal.
105

Working Principle
 Piezoelectric accelerometers are made up of single crystals.
These use the piezoelectric effect to measure the acceleration.
When applied to stress, these crystals generate a voltage which
is interpreted to determine the velocity and orientation.
 Capacitive accelerometers use a silicon micro-machined
element. Here capacitance is generated when acceleration is
sensed and this capacitance is translated into a voltage to
measure the velocity values.
 Modern accelerometers are the smallest MEMS, consisting of a
cantilever beam with proof mass. Accelerometers are available
as two-dimensional and three-dimensional forms to measure
velocity along with orientation. When the upper-frequency
range, high-temperature range, and low packaged weight are
required, piezoelectric accelerometers are the best choice.
106

Applications
The Applications of Accelerometer sensor are as follows:
 For inertial navigation systems, highly sensitive accelerometers are used.
 To detect and monitor vibrations in rotating machinery.
 To display images in an upright position on screens of digital cameras.
 For flight stabilization in drones.
 Accelerometers are used to sense orientation, coordinate acceleration, vibration, shock.
 Used to detect the position of the device in laptops and mobiles.
 High-frequency recording of biaxial and triaxial acceleration in biological applications for
discrimination of behavioral patterns of animals.
 Machinery health monitoring.
 To detect faults in rotator machines.
 These are also used for building and structural monitoring to measure the motion and
vibration of the structure when exposed to dynamic loads.
 To measure the depth of CPR chest compressions.
 Navigation systems make use of accelerometer sensors for knowing the direction.
 Remote sensing devices also use accelerometers to monitor active volcanoes.
107

Uses/Examples
 Some of the examples of the applications of accelerometer
sensor are Aircrafts, missiles, Quake-catcher network for
scientific research of earthquakes, pumps, fan, rollers,
compressors, Zoll’s AED plus, footpods, Intelligent
compaction rollers, airbag deployment system, electronic
stability control system in automobiles, tilting trains,
Gravimetry, camcorders, Glogger VS2, mobile phones etc…
108

GPS Sensor
109

GPS Sensor
 As we know GPS stands for Global Positioning System. The
system contains satellites and ground based control
installations. GPS sensor consists of surface mount chip
which processes signals from GPS satellites using a small
rectangular antenna, often mounted on the top of the GPS
chip.
• GPS module is usually small board on which GPS sensor is
mounted with additional components.
• GPS receiver is a device which includes data display and other
components such as memory for data storage in addition to
GPS module.
110

GPS Sensor
111

GPS Sensor
 The figure-1 depicts breakout board along with GPS sensor
offered by Adafruit industries. GPS system consists of three
segments viz. space segment, control segment, user
segment. Space segment contains about 31 satellites as of
August 2018 which are located in the orbit about 12,500
miles above earth. Hence each of these satellites circle two
times in 24 hours. Control segment contains command,
control and monitoring stations. USer segment consists of
receiving devices (e.g. both government and private).
112

GPS Sensor Working
113

GPS Sensor Working
 ➤As shown in figure-2, about four satellites are needed to
determine a position on the earth in 3 dimensional space.
Each of these satellites carry multiple atomic clocks which
maintain precise time and pseudo random number
generator in the form of linear feedback shift register.
➤GPS receiver can distinguish signals from atleast four
satellites by comparing their received pseudo random bit
sequences and can calculate receiver's distance to each of
these satellites by comparing arrival times of satellite
signals.
➤Distance = transit time (sec) x speed of light (meter/sec)
114

GPS Sensor Working
 ➤GPS satellites transmit on several frequencies simultaneously.
One such frequency known as L1 (1575.42 MHz) is used for civilian
applications where as the other frequency L2 (1227.6 MHz) is used
for military applications. Refer GPS and GNSS frequency bands >>
for more information on gps and gnss frequencies.
➤GPS module housing GPS sensor requires DC power supply. It
starts outputting data as soon as it identifies the satellites within
its range. The data follows plain ASCII protocol known as NMEA
protocol. The transmission rate is either 4800 bps or 9600 bps and
uses {8 bits, no parity, 1 stop bit} for decoding. The data blocks
are known as sentences which are of about 80 characters in
length. Refer GPS Sentences >> for more information. These gps
sentences contain latitude, longitude, altitude and data recording
time. These sentences are decoded by connecting microcontroller
with GPS module and writing small program.
115

Bluetooth Sensors
116

Bluetooth Sensors
117

Bluetooth Sensors
 At the moment, the world has been made more brilliant by the rapid
advancements in technology. New devices and ideas have risen
continuously, thereby improving the prevailing technologies and
generating new market sections. Similarly, Bluetooth technological
advances have contributed to the birth of Bluetooth Low Energy
(BLE), also referred to as Bluetooth Smart. The Bluetooth Low Energy
is a short-range, low-power with a less-data-rate wireless
communication protocol developed by the Bluetooth Special Interest
Group (SIG). Its encrusted protocol stack is designed in such a way
that it competently transfers insignificant amounts of data with less
consumption of power. Due to this, Bluetooth Low Energy is the
most preferred wireless protocol for battery-operated applications.
This article will explore the technical features of Bluetooth sensors,
how to connect and use Bluetooth sensors, how Beacon sensors can
be used for business, and how to read and control sensor data in
Arduino using Bluetooth.
118

Transmit Data using Bluetooth
Beacon sensors
 Bluetooth Beacon sensors are small transmitters that
broadcast signals to close portable devices using Bluetooth
Low Energy technology. They have an action range of
around 90 meters and can only transmit data but cannot
receive it. Once the sensor detects the nearby devices, it
sends digital messages to the targeted devices. Currently,
beacons are used proportionally with mobile applications.
These mobile applications obtain a unanimously unique
identifier to perform several functions, such as triggering a
location-based action and tracking customers.
119

Transmit Data using Bluetooth
Beacon sensors
120

Technical Features of a Bluetooth
Sensor
a) Radio interface
 The Bluetooth IoT sensors work with the same spectrum
range of between 2.400–2.4835 GHz ISM band as classic
Bluetooth technology. The only difference is that Bluetooth
Low Energy uses a different set of channels. It has forty 2-
MHz channels, whereas classic Bluetooth has seventy-nine
1-MHz channels. The Gaussian frequency shift modulation
is used to transmit data within a channel in the BLE
technology. It has a bit rate of 1 Mbit/s but with an option
in Bluetooth 5 of 2 Mbit/s. Also, it has a maximum transmit
power of 10 mW and 100 mW in Bluetooth 5.
121

Sensor
b) Advertising and discovery
 Bluetooth Low Energy sensors are spotted through a
technique based on broadcasting advertising packets. It is
usually done using 3 distinct frequencies to decrease
interference. The advertising device sends packets of not
less than one of the three frequencies with a repetition
period termed as the advertising interval. In each
advertising interval, there is an addition of a random delay
of 10 milliseconds that reduces the chance of numerous
consecutive collisions. The scanner attends to the
frequencies for a period termed as the scan window, which
is occasionally recurrent after each scanning interval.
122

Sensor
c) Battery impact
 Bluetooth Low Energy sensors are specially designed to
work even with shallow power consumption. Various power
necessities are required for devices with central and
peripheral roles. A study conducted by a beacon software
company Aislelabs conveyed that computer peripherals, for
instance, propinquity beacons, regularly function for up to 2
years using a 1,000mAh coin cell battery. The Bluetooth
Low Energy protocol makes this possible due to its power
efficiency. BLE transmits small packets; hence it’s ideal for
high and audio bandwidth data compared to Bluetooth
Classic.
123

Sensor
d) 2M PHY
 A new doubled symbol rate transmission mode has been
introduced by Bluetooth 5. Initially, Bluetooth Low Energy
sensors only transmitted 1 bit per symbol, but with
Bluetooth 5, they can data with double rates. However, the
new transmission mode pairs the bandwidth to 2 MHz from
about 1 MHz, making more intrusions on the edge areas.
The ISM frequency band segmentation has 40 channels
with a spaced distance of 2 MHz, which is essentially
different from the Bluetooth 2 EDR.
124

Technical Features of a
Bluetooth Sensor
e) GATT operations
 The GATT protocol is essential to the user as it offers several
commands regarding the discovered information about the
server. These commands include:
 Discovering UUIDs for each principal services
 Finding a given UUID for every service
 Finding subordinate services for a given principal service
 Discovering every feature for a specific service
 Finding features that match a specified UUID
 Reading all signifiers for a precise distinctive
125

Pairing a Bluetooth Sensor with a
Smartphone
 the steps followed when pairing Bluetooth-compatible sensors
using a smartphone. The Aventura receives the sensor pairing data
together with the settings once the pairing process is complete.
a) Ensure that (Connect) is on, then from the (MENU) tap (Device)
b) Start the sensor
 Once the Bluetooth smart sensor signal is detected, it displays a
message on the smartphone.
 To complete the pairing process of the already displayed sensor,
tap (Pairing).
 Press (Skip) if the gadget’s name is dissimilar from the expected,
then tap (Pairing) again. Repeat this occasionally till the anticipated
device is shown.
 When using the Bluetooth le sensor to pair, the sensor name is
displayed with an “A.”
 Over 18 distinct sensor identifications, including the P.C, can be
paired.
126

Pairing a Bluetooth Sensor with
a Smartphone
c) Establish the tire circumference for any sensor with speed
measurements
 Press (Device), and also tap the Sensor name > [Tire
Circumference]. Tire circumference is the approximate length of
the outer rim in each tire. Sensors that cannot measure speed
are never displayed.
 The tire size list is displayed once tapping is done. The tire
circumference is selected per the tire size shown on the tire
side.
 Original value: 2096 mm
 To any Bluetooth door sensor capable of speed measurements,
it is recommendable to set the tire circumference.
 It is possible to cancel the pairing and changed the device
names from this screen.
127

Pairing a Bluetooth Sensor with
a Smartphone
 After following all those steps, the pairing process of the Bluetooth
sensor is now complete.
 Repeat the same procedure when pairing with another Bluetooth sensor.
 After completing the pairing process, it is essential to mount the
Bluetooth motion sensor close to you. Also, follow the guidelines written
on the individual sensor’s instruction manual appropriately to determine
the suitable place to mount the sensor.
 Important Information
 Pair every usable sensor.
 Never pair Bluetooth smart sensors in the exact location or at any venue
with many other users. Doing this can make the sensors pair up with
other irrelevant devices. A Bluetooth mesh sensor can epitomize a sole
physical BLE sensor.
 When working with third-party Bluetooth sensors, only an Android
smartphone can transfer data to the Aventura, whereas an iPhone cannot.
128

RANGE sensor
129

Working principle of Range
sensors
 The distance between the object and the robot hand is
measured using the range sensors Within it is range of
operation.
 The calculation of the distance is by visual processing. Range
sensors find use in robot navigation and avoidance of the
obstacles in the path.
 The - location and the general shape characteristics of the part
in the work envelope of the robot S done by special
applications for the range sensors.
 There are several approaches like, triangulation method,
structured lighting approach and time-of flight range finders
etc. In these cases the source of illumination can be light-
source, laser beam or based on ultrasonic.
130

Triangulation Method:
 The object is swept over by a
narrow beam of sharp light.
 The sensor focused on a
small spot of the object
surface detects the reflected
beam of light.
 If ‗8‘is the angle made by
the ill source and the sensor,
the distance
131

Structured Lighting Approach:
 This approach consists of projecting a light pattern the
distortion of the pattern to calculate the range. A pattern in use
today is a sheet of light generated narrow slit.
 As illustrated in. Figure, the intersection yields a light Stripe
which is viewed through a television camera displaced a
distance B from the light source.
 The stripe pattern is easily analysed by a computer to obtain
range information. For example, an inflection indicates a
change of surface, and a break corresponds to a gap between
surfaces.
 Specific range values are computed by first calibrating the
system. One of the simplest arrangements is shown in Figure,
which represents a top view of Figure.
 In this, arrangement, the light source and camera are placed at
the same height, and the sheet of light is perpendicular to the
line joining the origin of the light sheet and the centre of the
camera lens.
132

RF Beacon
133

RF Beacon
 An RF Beacon is a circuit that produces a continuous pulse
that helps with tracking down an item or vehicle. One use
for such a beacon would be to locate a rocket when it
comes back down too far away to be seen. In this DIY
Hacking project, we will use a 433 MHz RF transmitter and a
pair of 555 astable oscillators to create an RF beacon.
134

RF Beacon Circuit Schematic
135

How Does the RF Transmitter
Work
 The RF beacon consists of three main units; A low frequency 555
oscillator, an audio (high frequency) oscillator, and an RF 433MHz
module. The first unit, a low-frequency oscillator, creates a pulse at
a frequency of approximately 1Hz which has an extremely large
duty cycle (close to 99.9%). This signal is then inverted thanks to Q1
in the form of a NOT gate, this creates a pulse with a duty cycle
near 0.01%. The low duty cycle pulse is connected to the RESET of
an audio 555 oscillator. When the output from the low-frequency
oscillator stage (after Q1) becomes 0V, the audio oscillator (IC2), is
disabled and the result is no audio signal being produced. When
the output of the low-frequency oscillator becomes VCC then the
audio oscillator (IC2) is enabled and produces an audio able tone.
This signal is inverted and then fed into the RF module which emits
a tone on the 433MHz spectrum which can easily be picked up by
receivers.
136

How Does the RF Transmitter
Work
 The circuit can be built using through hole techniques
including PCB, solderless breadboard, stripboard, and even
matrix board. While the circuit shown here is rather large, it
can easily be shrunk down using surface mount
components. That way, the circuit can easily be fitted onto
small drones and RC planes while also keeping weight
down to add RF tracking capabilities. For this project, a
custom PCB has been designed to demonstrate the circuit
using CNC milling. All the files needed for this project can
be found here including the CNC code needed to make the
PCB: RF Beacon Project Files.
137

Ultrasonic Ranging Sensor
138

Ultrasonic Ranging Sensor
 An ultrasonic sensor is an instrument that measures the
distance to an object using ultrasonic sound waves.
An ultrasonic sensor uses a transducer to send and receive
ultrasonic pulses that relay back information about an
object’s proximity.
High-frequency sound waves reflect from boundaries to
produce distinct echo patterns.
139

Ultrasonic Sensors Works
 Ultrasonic sensors work by sending out a sound wave at a
frequency above the range of human hearing. The
transducer of the sensor acts as a microphone to receive
and send the ultrasonic sound. Our ultrasonic sensors, like
many others, use a single transducer to send a pulse and to
receive the echo. The sensor determines the distance to a
target by measuring time lapses between the sending and
receiving of the ultrasonic pulse.
140

141

 The working principle of this module is simple. It sends an ultrasonic
pulse out at 40kHz which travels through the air and if there is an
obstacle or object, it will bounce back to the sensor. By calculating
the travel time and the speed of sound, the distance can be
calculated.
Ultrasonic sensors are a great solution for the detection of clear
objects. For liquid level measurement, applications that use infrared
sensors, for instance, struggle with this particular use case because
of target translucence.
For presence detection, ultrasonic sensors detect objects regardless
of the color, surface, or material (unless the material is very soft like
wool, as it would absorb sound.)
To detect transparent and other items where optical technologies
may fail, ultrasonic sensors are a reliable choice.
142

Features
 Power supply: 5V DC.
 Effectual angle: <15°.
 Ranging distance: 25cm – 500 cm.
 Resolution: 1 cm.
 Ultrasonic Frequency: 40k Hz.
143

Hardware
 Connect this triple axis magnetometer breadkout module to
your Arduino/Crowduino I2C wires(SDA:A4, D18;SCL:A5,
D19)as below:
144

Technical characteristics
 Prismatic PVC reflecting translucent with protector in rigid
PVC welded by ultrasounds.
 Reinforcement in adhesive of reflecting and translucent
vinyl. Subjection in velcro and nylon rivets. Anti UV
processing.
145

Advantages
 Tone of light. Its yellow light tone allows you to see double
than with an amber light and triple than with a redorange
light.
 Color. The dominant colors in city (halogenous lamps) or in
the morning correspond to warm ranges.
 Barbolight beam diffuser has a different color that contrasts
a lot.
 Sparkle. The light emitted by the lantern is not distributed
in homogenous way, so it changes with respect to the rake,
producing an effect sparkle when it moves.
 Reflectivity. Beam diffuser is made of a high reflectivity
material so its visibility is very superior even without
emission of the lantern and only with security light.
 Volume. Its foldable systems allow being transported easily
146

Laser range sensor
147

Laser range sensor
 Laser distance sensors are designed for non-contact
distance measurements: laser gauges for measuring ranges
up to 10m, laser distance sensors for up to 270m. These
sensors are used for positioning and type classification in
machine building and handling equipment.
 Here are applications for detections, measurements or
positioning. What different laser sensors have in common
are the advantages that the use of laser light provides. A
first advantage is the high light intensity, which enables
very accurate measurement, positioning or detection (down
to nanometers). Another advantage is the measurement
speed; this is very high due to the use of light as a medium.
148

Different types of sensors that work
on the basis of laser light are:
 Laser distance sensors
 Displacement sensors
 Laser projectors
 Laser light curtains
 Laser photoelectric sensors
 Positioning lasers
 Laser edge detection sensors
149

1.Laser distance sensors
 Laser distance sensors measure distances and allow it to
take measurements at great distances. These distance
sensors work on the basis of the Time-Of-Flight (ToF)
principle, which means that the sensor emits a laser beam
and receives the reflection from it. The time that elapses
between sending and receiving the laser light ensures that
the laser distance sensor can internally determine the
distance. The distance over which the measurements can be
taken differs per series.
150

Working Principle of a LASER
Sensor
 In a LASER sensor, the measurement of distance is based on
the triangulation principle. By this principle, the LASER
beam will be incident on the object. LASER sensor would
strike the object as a small point; some part of the light will
be reflected back. The receiver of the sensor will detect the
position of this point. The angle of incidence will change
according to the distance and so will the position of the
LASER point in the receiver.
151

Working of LASER Sensor
 LASER beam is incident on the object which is to be sensed.
Since LASER is a highly focused beam of light, it would appear
as a small bright dot.
 When the LASER beam is incident on the object which is to be
sensed, some part of light would be reflected back by the
object. This reflected light is sensed by a receiver in the sensor,
say a photodiode. The sensor has internal circuitry that would
do the signal processing part.
 In signal processing, the time taken by the light to emit and the
time taken by the light to reflect back are calculated. The speed
of LASER light emission is fixed. So, the object’s distance from
the sensor can be calculated simply by using speed and time.
The sensor will generate an electrical signal according to the
distance sensed. This signal is either digital or analog.
152

2. Laser Displacement Sensors
 Displacement sensors are generally used to detect objects.
Displacement sensors are not aimed to measure distance. In
Displacement sensors, the sensor would emit LASER light. A
passing object would reflect the beam when the object
crosses the displacement sensors. This reflected beam
would make the sensor judge the received reflection as a
detection of the object.
 Displacement sensors are more versatile. Displacement
sensors can be used in thickness measurement also.
Displacement sensors can be used in profile measurements
and position measurements.
153

2. Laser Displacement Sensors
154

3. Laser Projector
 LASER projectors are LASERs that can project LASER light
on the desired surface. The projected light can determine
margins, dimensions, or position in an application. LASER
projectors are used in industries like textile or electronics.
LASER projectors are also used for presentations in offices,
classrooms, hotels, museums, showrooms, and attractions
to simulation applications.
155

4. LASER Photoelectric Sensors
 LASER photoelectric sensors are used where the processes
are carried out at high speed. For example,
counting/detecting the product. Because of their capacity
to detect objects at high speeds, they are also known as
trigger sensors.
156

5. LASER Edge Detection Sensors
 LASER edge detection sensors are used where inline
detection and counting one side of the product are needed.
The LASER edge detection sensors are mounted in the
production line. The LASER edge detection sensors are used
where thin sheets/plates must be detected on the basis of
thickness so as to limit accumulations and production
errors.
157

6. Laser Light Curtains
 These types of laser sensors consist of a transmitter and a
receiver. There is a barrier of parallel laser beams emitted
between the transmitter and receiver. Objects passing
through the barrier are detected and also measured.
158

7. Laser Positioning sensor
 These lasers are used for the positioning of the products.
The positioning laser transmits a projection and it does not
receive the reflection.
159

Advantages of LASER sensors
 The LASER sensor’s measurement is very accurate.
 LASER sensors have a high direction of the beam and a small
divergence angle of light.
 The level of brightness is high for LASER sensors.
 LASER sensors can range up to several kilometers.
 The frequency width for LASER sensors is smaller than ordinary
light.
 Contactless measurement is done by LASER sensors, so does
not interrupt the process.
 Digital, as well as analog outputs, are available for LASER
sensors.
 LASER sensors can be used in all industrial environments.
 Detects a wide range of materials.
 It is easy to install Laser sensors.
 Resistant to interference and environmental noise.
160

Disadvantages of LASER sensors
 LASER sensors are more expensive than analog measuring
devices.
 LASER sensors are very delicate because very precise
calibration needs to be maintained.
 In some processes, a very high level of precision is not
needed. Hence LASER sensors are not suitable there.
 LASER sensors can damage eyesight.
161

Applications of LASER sensors
 Location of object
 Quality control
 Aligning the railway track
 Measuring wire diameter
 Welding head position
 Measure brake rotor thickness
 Vehicle counting
 Limit recognition of the width and height of the vehicle
 Measuring the distance between two sheets
 Power tool control
 Checking wood thickness
 Deviation control in the process
 Quality Control
 check the wood thickness
162

UNIT II - MOTION, PROXIMITY AND RANGING SENSORS

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UNIT II - MOTION, PROXIMITY AND RANGING SENSORS