sensor types - · pdf fileoptical(photoelectric) sensors • all optical sensors use light...

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