Sensor and Transducers By-G/Michael G. - PowerPoint Presentation

Slide1

Sensor and Transducers

By-G/Michael G.Slide2

Definition

Devices which perform an input function are commonly called

Sensors

because they "sense" a physical change in some characteristic that changes in response to some excitation, for example heat or force and covert that into an electrical signal. Devices which perform an output function are generally called

Actuators

and are used to control some external device, for example movement.

Both sensors and actuators are collectively known as

Transducers

because they are used to convert energy of one kind into energy of another kind, Slide3

for example, a microphone (input device) converts sound waves into electrical signals for the amplifier to amplify, and a loudspeaker (output device) converts the electrical signals back into sound waves and an example of this type of I/O system is given below.Slide4

Common Transducers

Quantity being

Measured

Input Device

(Sensor)

Output Device

(Actuator)

Light Level

Light Dependent Resistor (LDR)

Photodiode

Photo-transistor

Solar Cell

Lights & Lamps

LED's & Displays

Fiber Optics

Temperature

Thermocouple

Thermistor

Thermostat

Resistive temperature detectors (RTD)

Heater

Fan

Force/Pressure

Strain Gauge

Pressure Switch

Load Cells

Lifts & Jacks

Electromagnet

Vibration

Position

Potentiometer

Encoders

Reflective/Slotted

Opto

-switch

LVDT

Motor

Solenoid

Panel Meters

Speed

Tacho

-generator

Reflective/Slotted

Opto

-coupler

Doppler Effect Sensors

AC and DC Motors

Stepper Motor

Brake

Sound

Carbon Microphone

Piezo-electric Crystal

Bell

Buzzer

LoudspeakerSlide5

Analogue and Digital Sensors

Analogue Sensors

Analogue Sensors

produce a continuous output signal or voltage which is generally proportional to the quantity being measured. Physical quantities such as Temperature, Speed, Pressure, Displacement, Strain etc. are all analogue quantities as they tend to be continuous in nature. For example, the temperature of a liquid can be measured using a thermometer or thermocouple which continuously responds to temperature changes as the liquid is heated up or cooled down.Slide6

Thermocouple used to produce an Analogue SignalSlide7

Digital Sensors

As its name implies,

Digital Sensors

produce a discrete output signal or voltage that is a digital representation of the quantity being measured.

Digital sensors produce a

Binary

output signal in the form of a logic "1" or a logic "0", ("ON" or "OFF"). This means then that a digital signal only produces discrete (non-continuous) values which may be outputted as a single "bit", (serial transmission) or by combining the bits to produce a single "byte" output (parallel transmission).Slide8

Light Sensor used to produce a Digital SignalSlide9

Signal Conditioning

Then amplification is part of signal conditioning. So when using analogue sensors, generally some form of amplification (Gain), impedance matching, isolation between the input and output or perhaps filtering (frequency selection) may be required before the signal can be used and this is conveniently performed by

Operational Amplifiers

.

Typical Op-amp FiltersSlide10

Position SensorsSlide11

Position Sensors

a variety of devices which are classed as

Input Devices

and are therefore called "Sensors" and in particular those sensors which are

Positional

in nature which means that they are referenced either to or from some fixed point or position. As their name implies, these types of sensors provide a "position" feedback.

One method of determining a position, is to use either "distance", which could be the distance between two points such as the distance travelled or moved away from some fixed point, or by "rotation" (angular movement). Slide12

The Potentiometer.

The most commonly used of all the "Position Sensors", is the

potentiometer

because it is an inexpensive and easy to use position sensor. It has a wiper contact linked to a mechanical shaft that can be either angular (rotational) or linear (slider type) in its movement, and which causes the resistance value between the wiper/slider and the two end connections to change giving an electrical signal output that has a proportional relationship between the actual wiper position on the resistive track and its resistance value. In other words, resistance is proportional to position.Slide13

Potentiometer Construction

The output signal (V out) from the potentiometer is taken from the center wiper connection as it moves along the resistive track, and is proportional to the angular position of the shaft.Slide14

Example of a simple Positional Sensing Circuit

While resistive potentiometer position sensors have many advantages: low cost, low tech, easy to use etc., as a position sensor they also have many disadvantages: wear due to moving parts, low accuracy, low repeatability, and limited frequency response.Slide15

Inductive Position Sensors.

One type of positional sensor that does not suffer from mechanical wear problems is the "Linear Variable Differential Transformer" or

LVDT

for short. This is an inductive type position sensor which works on the same principle as the AC transformer that is used to measure movement. It is a very accurate device for measuring linear displacement and whose output is proportional to the position of its moveable core.Slide16

The Linear Variable Differential TransformerSlide17

Inductive Proximity Sensors.

Another type of inductive sensor in common use is the

Inductive Proximity Sensor

also called an

Eddy current sensor

. While they do not actually measure displacement or angular rotation they are mainly used to detect the presence of an object in front of them or within a close proximity, hence the name proximity sensors.Slide18

Rotary Encoders.

Rotary Encoders

resemble potentiometers mentioned earlier but are non-contact optical devices used for converting the angular position of a rotating shaft into an analogue or digital data code. In other words, they convert mechanical movement into an electrical signal (preferably digital).

There are two basic types of rotary optical encoders,

Incremental Encoders

and

Absolute Position Encoders

.Slide19

Incremental Encoders

Incremental Encoders

, also known as quadrature encoders or relative rotary encoder, are the simplest of the two position sensors. Their output is a series of square wave pulses generated by a photocell arrangement as the coded disk, with evenly spaced transparent and dark lines called segments on its surface, moves or rotates past the light source. Slide20

Absolute Position Encoder

Absolute Position Encoders

are more complex than quadrature encoders. They provide a unique output code for every single position of rotation indicating both position and direction.Slide21

Temperature SensorsSlide22

Temperature Sensor Types

Contact Temperature Sensor Types -

These types of temperature sensor are required to be in physical contact with the object being sensed and use conduction to monitor changes in temperature. They can be used to detect solids, liquids or gases over a wide range of temperatures.

Non-contact Temperature Sensor Types

-

These types of temperature sensor use convection and radiation to monitor changes in temperature. They can be used to detect liquids and gases that emit radiant energy as heat rises and cold settles to the bottom in convection currents or detect the radiant energy being transmitted from an object in the form of infra-red radiation (the sun). Slide23

The Thermostat

The

Thermostat

is a contact type electro-mechanical temperature sensor or switch, that basically consists of two different metals such as nickel, copper, tungsten or aluminum etc. that are bonded together to form a

Bi-metallic strip

.Slide24

The Thermistor

The

Thermistor

is another type of temperature sensor, whose name is a combination of the words

THERM

-ally sensitive res-

ISTOR

. A thermistor is a type of resistor which changes its physical resistance with changes in temperature.

Most types of thermistor's have a

Negative Temperature Coefficient

of resistance or

(NTC)

, that is their resistance value goes DOWN with an increase in the temperature but some with a

Positive Temperature Coefficient, (PTC)

, their resistance value goes UP with an increase in temperature are also available.Slide25
Slide26

Resistive Temperature Detectors (RTD).

Another type of electrical resistance temperature sensor is the

Resistance Temperature Detector

or

RTD

. RTD's are precision temperature sensors made from high-purity conducting metals such as platinum, copper or nickel wound into a coil and whose electrical resistance changes as a function of temperature, similar to that of the thermistor. Also available are thin-film RTD's. These devices have a thin film of platinum paste is deposited onto a white ceramic substrate.Slide27

The Thermocouple

The

Thermocouple

is by far the most commonly used type of all the temperature sensing devices due to its simplicity, ease of use and their speed of response to changes in temperature, due mainly to their small size. Thermocouples also have the widest temperature range of all the temperature sensors from below -200

o

C to well over 2000

o

C.Slide28

Thermocouple Amplification

The type of amplifier, either discrete or in the form of an Operational needs to be carefully selected, because good drift stability is required to prevent recalibration of the thermocouple at frequent intervals. This makes the chopper and instrumentation type of amplifier preferable for most temperature sensing applications.

Other types of

Temperature Sensor

not mentioned here include, Semiconductor Junction Sensors, Infra-red and Thermal Radiation Sensors, Medical type Thermometers, Indicators and Color Changing Inks or Dyes.Slide29

The Light SensorSlide30
Slide31

Light Sensor

A

Light Sensor

generates an output signal indicating the intensity of light by measuring the radiant energy that exists in a very narrow range of frequencies basically called "light", and which ranges in frequency from "Infrared" to "Visible" up to "Ultraviolet" light spectrum.

The light sensor is a passive devices that convert this "light energy" whether visible or in the infrared parts of the spectrum into an electrical signal output. Light sensors are more commonly known as "Photoelectric Devices" or "Photo Sensors" because the convert light energy (photons) into electricity (electrons).Slide32

Group of light sensors

Photo-conductive Cells -

These photo devices vary their electrical resistance when subjected to light.

Photo-emissive Cells -

These are photo devices which release free electrons from a light sensitive material such as

caesium

when struck by a photon of sufficient energy.

Photo-voltaic Cells -

These photo devices generate an EMF in proportion to the radiant light energy received and is similar in effect to photoconductivity.

Photo-junction Devices -

These photo devices are mainly true semiconductor devices such as the photodiode or phototransistor which use light to control the flow of electrons and holes across their PN-junction. Slide33

The Photoconductive Cell

A

Photoconductive

light sensor does not produce electricity but simply changes its physical properties when subjected to light energy. The most common type of photoconductive device is the

Photo resistor

which changes its electrical resistance in response to changes in the light intensity.

The Light Dependent ResistorSlide34

The Light Dependent Resistor CellSlide35

Photo junction Devices

Photo junction Devices

are basically

PN-Junction

light sensors or detectors made from silicon semiconductor PN-junctions which are sensitive to light and which can detect both visible light and infrared light levels. Photo-junction devices are specifically made for sensing light and this class of photoelectric light sensors include the

Photodiode

and the

Phototransistor

.Slide36

Photo-diode Construction and CharacteristicsSlide37

Photo-diode Amplifier CircuitSlide38

The Phototransistor

An alternative photo-junction device to the photodiode is the

Phototransistor

which is basically a photodiode with amplification. The Phototransistor light sensor has its collector-base PN-junction reverse biased exposing it to the radiant light source.Slide39

Photo-transistor Construction and CharacteristicsSlide40

Photo-Darlington

Photo Darlington

transistors use a second bipolar NPN transistor to provide additional amplification or when higher sensitivity of a photo detector is required due to low light levels or selective sensitivity, but its response is slower than that of an ordinary NPN phototransistor.Slide41

Photovoltaic Cells.

Photovoltaic cells

are made from single crystal silicon PN junctions, the same as photodiodes with a very large light sensitive region but are used without the reverse bias. They have the same characteristics as a very large photodiode when in the dark. When illuminated the light energy causes electrons to flow through the PN junction and an individual solar cell can generate an open circuit voltage of about 0.58v (580mV). Solar cells have a "Positive" and a "Negative" side just like a batterySlide42

Characteristics of a typical Photovoltaic Solar Cell.Slide43

The Sound sensorSlide44

Sound Transducer

Sound

is the general name given to "acoustic waves" that have frequencies ranging from just 1Hz up to many tens of thousands of Hertz with the upper limit of human hearing being around the 20 kHz, (20,000Hz) range.Slide45

Sound Wave Relationship

Where:

Wavelength is the time period of one complete cycle in Seconds.

Frequency is the number of wavelengths per second in Hertz.

Velocity is the speed of sound through a transmission medium in m/s

-1

.Slide46

The Microphone Transducer

The

Microphone

, also called a "mic", is a sound transducer that can be classed as a "sound sensor".Slide47

Actuators Slide48

Actuators

Actuators convert an electrical signal into a corresponding physical quantity such as movement, force, sound etc. An actuator is also a transducer because it changes one type of physical quantity into another and is usually activated or operated by a low voltage command signal.

Actuators can be classed as either binary or continuous devices based upon the number of stable states their output has.Slide49

The Electromechanical Relay

The term

Relay

generally refers to a device that provides an electrical connection between two or more points in response to the application of a control signal. The most common and widely used type of electrical relay is the electromechanical relay or EMR.Slide50

Electromechanical Relay ConstructionSlide51

Relay Contact Configurations

Where:

C is the Common terminal

NO is the Normally Open contact

NC is the Normally Closed contactSlide52

The Solid State Relay.

To overcome these disadvantages of the electrical relay, another type of relay called a

Solid State Relay

or (

SSR

) for short was developed which is a solid state contactless, pure electronic relay. It has no moving parts with the contacts being replaced by transistors,

thyristors

or

triacs

.Slide53

The Linear Solenoid

Another type of electromagnetic actuator that converts an electrical signal into a magnetic field is called a

Solenoid

.

A

Linear Solenoid

is an electromagnetic device that converts electrical energy into a mechanical pushing or pulling force or motion.Slide54

When an electrical current is passed through the coils windings, it behaves like an electromagnet and the plunger, which is located inside the coil, is attracted towards the center of the coil by the magnetic flux setup within the coils body, which in turn compresses a small spring attached to one end of the plunger. The force and speed of the plungers movement is determined by the strength of the magnetic flux generated within the coil.Slide55

Pull-type Linear Solenoid ConstructionSlide56

Rotary Solenoids

Most electromagnetic solenoids are linear devices producing a linear back and forth force or motion. However, rotational solenoids are also available which produce an angular or rotary motion from a neutral position in either clockwise, anti-clockwise or in both directions (bi-directional).Slide57

DC Motor

Electrical

Motors

are continuous actuators that convert electrical energy into mechanical energy in the form of a continuous angular rotation that can be used to rotate pumps, fans, compressors, wheels, etc. Slide58

Most used Actuators

Brushed Motor

Brushless Motor

Stepper motor

Servo Motor Slide59

The Loudspeaker Transducer

Loudspeakers are also sound transducers that are classed as "sound actuators" and are the exact opposite of microphones. Their job is to convert complex electrical analogue signals into sound waves being as close to the original input signal as possible.Slide60

The principle of operation of the Moving Coil Loudspeaker is the exact opposite to that of the "Dynamic Microphone"Slide61

SMART SENSORSSlide62

What is a smart sensor?

Smart sensors are "sensors and instrument packages that are microprocessor driven and include features such as communication capability and on-board diagnostics that provide information to a monitoring system and/or operator to increase operational efficiency and reduce maintenance costs."Slide63

General Architecture of Smart Sensor

Sensing element/transduction element,

Amplifier,

Sample and hold,

Analog multiplexer,

Analog to digital converter (ADC),

Offset and temperature compensation,

Digital to analog converter (DAC),

Memory,

Serial communication

ProcessorSlide64

Types of Smart Sensors

Optical Sensor

Infrared detector array

Accelerometer

Integrated multisensorSlide65

Optical Sensor

Optical sensor is one of the examples of smart sensor, which are used for measuring exposure in cameras, optical angle encoders and optical arrays. Similar examples are load cells silicon based pressure sensors.Slide66

Infrared detector array

Integrated sensor is the infrared detector array developed at the solid laboratory of the University of Michigan.

The Infrared-sensing element was developed using polysilicon -Au thermocouples and thin film dielectric diaphragm to support the thermocouples.

On-chip multiplexer was fabricated by using silicon gate MOS processing.

This detector operates over a temperature range of 0 to 100 degree centigrade with a 10msec response time. Slide67

Accelerometer

Accelerometer fabricated at the IBM Research laboratory at San Jose California, which consists of the sensing element and electronics on silicon.

The accelerometer itself is a metal-coated SiO2 cantilever beam that is fabricated on silicon chip where the capacitance between the beam and the substrate provides the output signal.Slide68

Integrated multisensor

Integrated multisensor chip developed at the electronics research Laboratory University of California.

This chip contains MOS devices for signal conditioning with on chip sensor, a gas flow sensor, an infrared sensing array, a chemical reaction sensor, a cantilever beam, accelerometer, surface acoustic wave vapor sensor, a tactile sensor array and an infrared charge coupled device imager.

This chip was fabricated using conventional silicon planer processing, silicon micromachining and thin deposition techniques.Slide69

Advantages

Minimum Interconnecting Cables

High Reliability

High Performance

Easy to Design, Use and Maintain

Scalable -Flexible System

Small Rugged Packaging

Minimum CostSlide70

Applications

Bluetooth Smart Sensor Module Rear Panel.

In-chamber and on-wafer sensors.

Monitoring of Temperature Using Smart Sensors Based on CAN Architecture.

Compatible sensors with microprocessors.

Smart sensors vie for vision applications: smart sensors can provide the functionality needed for simple, low-cost machine-vision applications.

A Smart Sensor Architecture for Marine Sensor NetworksSlide71

Conclusion

Smart Sensors has developed and proved a new miniaturized Smart Sensor Network Measurement System, which represents a paradigm shift from a centralized to a distributed processing measurement approach.

It significantly reduces the number and lengths of cables, the components size, and system weight. It provides greater flexibility in design, configuration and installation.

All of these advantages translate into cost savings throughout the life of a program.Slide72

Sensor Application Slide73

ApplicationLevel Measurement

in Large Vessels (Tanks, Silos)

Sensor

3RG61 13

Compact Range IIISlide74

Application anti-Collision

Sensor

3RG60 14

Compact Range ISlide75

ApplicationLevel Measurement in

Small Bottles

Sensor

3RG61 12

Compact Range IIISlide76

Application

height Sensing

Sensor

3RG60 13

Compact Range IISlide77

Application

Quality Control

Sensor

3RG61 12

Compact Range IIISlide78

Application

Breakage Sensing

Sensor

3RG61 12

Compact Range ISlide79

Application

Bottle Counting

Sensor

3RG62 43

Thru BeamSlide80

Application

Object Sensing

Sensor

3RG60 12

Compact Range IISlide81

Application

Vehicle Sensing and

Positioning

Sensor

3RG60 14

Compact Range IIISlide82

Application

Stack Height Sensing

Sensor

3RG60 13

Compact Range IISlide83

Application

Contour Recognition

Sensor

3RG61 13

Compact Range IIISlide84

ApplicationDiameter Sensing and

Strip Speed Control

sensor

3RG61 12

compact Range IIISlide85

Application

People Sensing

Sensor

3RG60 12

Compact Range IISlide86

Application

Wire and Rope Breakage Monitoring

Sensor

3RG60 12

Compact Range ISlide87

Application

Loop Control

Sensor

3RG60 15

Compact Range IISlide88

ApplicationVerifying Objects in Clear Bottles

Sensor

M12 thru BeamSlide89

Application

Flow of Pallets Carrying Bottles

Sensor

40 Retro reflectiveSlide90

ApplicationCounting Cans

Sensor

K50 Polarized

Retro reflectiveSlide91

Application

Counting Bottles

Sensor

SL18 Retro reflectiveSlide92

ApplicationCounting Cartons

Sensor

K65 Retro reflectiveSlide93

Application

Car Wash

Sensor

SL Thru BeamSlide94

ApplicationReading Reference Marks for Trimming

Sensor

C80 Mark SensorSlide95

ApplicationDetecting Persons

Sensor

K50 Retro reflectiveSlide96

ApplicationControlling Parking Gate

Sensor

SL Retro reflectiveSlide97

ApplicationEnd of Roll Detection

Sensor

K31 DiffuseSlide98

ApplicationDetecting Tab Threads

Sensor

KL40 Fibber OpticSlide99

ApplicationDetecting Caps on Bottles

Sensor

K20 Diffuse with Background Suppression and K31 thru BeamSlide100

ApplicationCounting Packages

Sensor

K80 Retro reflectiveSlide101

Application

Detecting Components inside Metal Can

Sensor

K50 Background

SuppressionSlide102

ApplicationDetermining Orientation of IC Chip

Sensor

L50 Laser with Background SuppressionSlide103

Application

Detecting Items of Varying Heights 

Sensor

K80 Background

SuppressionSlide104

Application Detecting Orientation of IC Chip

Sensor

Colour Mark or Fibber

OpticSlide105

Application Controlling Height of a Stack

Sensor

SL Thru BeamSlide106

Application Detecting Jams on a Conveyor

Sensor

K50 Retro reflectiveSlide107

Application Counting Boxes Anywhere on a Conveyor

Sensor

SL18 Right Angle

Retro reflectiveSlide108

ApplicationCounting IC Chip Pins

Sensor

KL40 Fibber OpticSlide109

Application

Batch counting and Diverting Cans without Labels

Sensor

K40 PolarizedSlide110

Application

Detecting Presence of Object to Start a Conveyor

Sensor

K35 Retro reflectiveSlide111

Application Detecting Reflective Objects

Sensor

K80 Polarized

Retro reflectiveSlide112

ApplicationVerifying Liquid in Vials

Sensor

K35 Fibber OpticSlide113

Application Verifying Screws are Correctly Seated

Sensor

KL40 Fibber OpticSlide114

ApplicationVerifying Cakes are Present in Transparent Package

Sensor

KL40 Fibber OpticSlide115

Application Verifying Lipstick Height before Capping

Sensor

M5 or M12 thru BeamSlide116

Application

Detecting Labels with Transparent Background

Sensor

G20 Slot SensorSlide117

Application

Monitoring Objects as they Exit Vibration Bowl

Sensor

K35 Fibber

OpticSlide118

Application

Detecting the Presence of a Broken Drill Bit

Sensor

12 mm Normal

RequirementsSlide119

ApplicationDetecting Milk in Cartons

Sensor

Capacitive Slide120

Application

Controlling Fill level of solids in a bin

Sensor

CapacitiveSlide121

ApplicationDetecting Full Open or

Closed Valve Position

Sensor

12mm or 18mm Extra

DutySlide122

ApplicationDetecting Presence of

Can and Lid

Sensor

30mm Normal Requirements or UBERO, 18mm Normal Requirements Gating SensorSlide123

ApplicationDetecting Broken Bit on Milling Machine

Sensor

18 mmSlide124

Thank you…..