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Sensor Sensor
typestypes
Automatic Control System
Automatic ControlSystem Construction
• Material or Power
• Object
• Output Signal
• Sensor
• Disturbances
• Converter
• Measuring Device
• Controller
• Industry Controller
• Executive Device
Graphic Symbols- Sensors and
Detectors
– PROXIMITY SENSOR
– PROXIMITY DEVICE
(FUNCTIONAL SYMBOL)
– CAPACITIVE CRYSTAL SET
TACTILE SENSOR -
– TACTILE SENSOR WITH NORMAL
CLOSED CONTACT
– PROXIMITY SENSOR WITH
NORMAL OPEN CONTACT
– IRON SENSOR
CONTACTRON
SENSORS
SELECTION
(CLASSIFICATION)
1. Contact versus Non-contact
• Contact sensor : There is physical contact
betwen the sensor an the parametr it
measures
• Non-contact sensor : Also called
proximity sensors. Proximity indicates that
the object is near, but contact is not
required.
Contact Sensor
Non- Contact Sensor
2. Digital (binary) versus Analog• Digital sensors
– Have two states: on or off
– Detect presence/absence of object
– Counting such as used in a rotary encoder
• Analog sensors
– They sense continuous variables (temp, pressure) and provide a continuous (usuallylinear) voltage or current according to aninput/output transfer function.
– More complex than digital and can providemore information.
3. Principles and Designs
• Sensor principles
– Inductive
– Capacitive
– Resistive
• Sensor designs
– Extrinsic
– Intrinsic
4. Digital Sensors
• Switches
• Optical (photoelectric) sensors
• Encoders
• Ultrasonic sensors
• Inductive sensors
• Capacitive sensors
5. Industrial sensors• Proximity
– Mechanical
– Optical
– Inductive/Capacitive
• Position/Velocity
– Potentiometr
– LVDT
– Encoders
– Tachogenerator
• Force/Pressure
• Vibration/Acceleration
InductiveInductive
sensorssensors
Types of inductive sensorsTypes of inductive sensors
�� proximityproximity
�� movementmovement
I. I. Schematic diagramSchematic diagram
metal generatorliminal
construction
with hysteresis
output
amplifier
output
signal
ProximityProximity sensorssensors
II. Principle of workingII. Principle of working
metalliminal
construction
with hysteresis
generator output
amplifier
output
signal
ProximityProximity sensorssensors
IIIIII. Parameters. Parameters
�� Nominal zone of workingNominal zone of working
Trip - out
Switches on
Metal plate
Inductive sensor
Hysteresis
Zone of working
ProximityProximity sensorssensors
�� Frequency of jumperingFrequency of jumpering
�� Real zone of workingReal zone of working
�� Working zone of actionWorking zone of action
Sensor
Traffic trend
Measuring plate St37
�� Hysteresis of jumperingHysteresis of jumpering
�� Corrective coeficiencCorrective coeficienceess
�� RepeatabilityRepeatability
�� Temperature of workingTemperature of working
�� Admission Admission
�� Residual voltage Residual voltage
�� Residual currentResidual current
Movement sensorsMovement sensors
I. I. Schematic diagramSchematic diagram
Movement sensorsMovement sensors
II. Principle of workingII. Principle of working
Movement sensorsMovement sensors
IIIIII. Parameters. Parameters
� ZZone of workingone of working
Trip - out
Switches on
Metal plate
Inductive sensor
Hysteresis
Zone of working
�� Corrective coeficiencCorrective coeficienceess
� HHysteresis of frequencyysteresis of frequency
�� LiminalLiminal frequenciesfrequencies
�� MMaximum frequency of jumperingaximum frequency of jumpering
�� TTime of decelerationime of deceleration
lowering speed
Increase speed
Out
IV. Symbol ofIV. Symbol of inductiveinductive sensorssensors
V. V. ExamplExampleses of of inductiveinductive sensorsensor
VI. InductiveVI. Inductive sensorsensor inin useuse
Quantity control
Detection unevenness on packaging
VI. InductiveVI. Inductive sensorsensor inin useuse
Control of screw tight the screws
CapacitiveCapacitive
sensorssensors
CapacitiveCapacitive sensorssensors
I. I. Schematic diagramSchematic diagram
object
screenactive surface
periphery of oscillator comparator amplifier
CapacitiveCapacitive sensorssensors
II. Principle of workingII. Principle of working
periphery of
oscillatoramplifiercomparator
OO
bb
jj
ee
cc
tt
IIIIII. . Symbol ofSymbol of capacitivecapacitive sensorsensors s
IIVV. . CapacitiveCapacitive sensorsensor inin useuse
�� SiliconSilicon WaferWafer deposition & etchingdeposition & etching
�� SiliconSilicon WaferWafer proximityproximity
�� WaferWafer cuttingcutting//processingprocessing
�� Robot armRobot arm controlcontrol
�� ComputerComputer hardhard discdisc drivedrive
�� Printing Press/PhotocopiersPrinting Press/Photocopiers
�� ToolingTooling parallelismparallelism//alignmentalignment
IIVV. . CapacitiveCapacitive sensorsensor inin useuse
Detection of movement
Detection of position
IIVV. . CapacitiveCapacitive sensorsensor inin useuse
Counting of
rotational speedSteering mechanical
process
Optical Optical
sensorssensors
Optical (Photoelectric) Sensors
• All optical sensors use light to senseobjects.
• Operation method:- Lasers, Incandescend bulbs, or Light emitting diodes
(LEDs) are used as light source
- The light source is turned off and on (modulation) at a high frequency (could be as hight as several kHz)
- A photodetector senses the pulsed light
- The light emitter and receiver are turned to themodulation frequency.
Example of Sensor using LED as a
light source
Types of Optical Sensors
• Reflective (Diffuse) Sensors
• Retroreflective Sensors
• Thru-beam Sensors
• Polarizing Photo Sensors
• Convergent Photo Sensors
• Fiber Optic Sensors
• Laser Sensors
Reflective (Diffuse) Sensors
T - Transmitter
R - Receiver
Transmitter and receiver are
combined into one casing
Work relies on the reflective surface on the target to
reflect the light from the transmitter to the receiver
T
R
OBJECT
Advantages
• Singular casing (Transmitter + Receiver)
• Objects detection with high reflectparameter (0,6 - 0,9)
Disadvantages
• Low detecting distance
• Sensitive to colour and quality
• Sensitive to background
• Dead zone
Retroreflective Sensors
Transmitter and receiver are combined into one
casing
Make use of a reflector to reflect the light from
the transmitter to the receiver
T
R
OBJECT
REFLECTOR
Advantages
• Easy instalation
• Singular casing ( Transmitter + Receiver)
• Good working zone
Disadvantages
• Sensitive to lights objects
• Use reflector
• Dead zone
Thru-beam Sensors
System has a separate transmitter and receiver
It’s capable of sensing very smallobject by narrowing the lightbeam
T R
OBJECT
Advantages
• Detection for long distance
• Lack of dead zone
• Detection light objects
• Detection in several environment
Disadvantages
• Large separate casings
• Problems with instalation ( set- up
Transmitter and Receiver)
Typical Application
• Detecting the presence or absence of an object
• Positioning and counting
• Detection the end of travel of an object
• Packaging machinery
• Sorting and labelling machinery
• Textile machinery
• Pharmaceutical
• Small part detection
• High speed detection
• Door controls
Parameters
- Operating Temperature (10°C - +50°C)
- Vibration
- Supply Voltage (10 – 30 VDC or 230 VAC)
- Detecting Distance
- Output Current
- Max. Switching Frequency
- Degree of Protection
- Hysteresis
Encoders
An encoder is a device that senses a
modification of speed and position and
converts it to a digital value
There are two main types of rotary
encoders:
- Incremental
-Absolute
Principle of working
The light from Light Source shines through the lines on disk
and Grid Assembly and is then sensed by photo detector
Construction of encoder’s disk:
Incremental encoders:
An incremental encoder generates a series of
square waves
Encoders transform rotary movement into a sequence of
electrical pulses
There are two main types of incremental
encoders:
-Tachometer
- Quadrature
Absolute encoder
An absolute encoder provides a word of output with a
qunique pattern that represents each position.
The output is proportional to the angle of the shaft
Principle of working
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