1. Sensor and Transducers
By-G/Michael G.

2. 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,

3. 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.

4. Quantity being Measured Output Device (Actuator)
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
Loudspeaker

5. 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.

6. Thermocouple used to produce an Analogue Signal

7. 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).

8. Light Sensor used to produce a Digital Signal

9. 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 Filters

10. Position Sensors

11. 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).

12. 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.

13. 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.

14. 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.

15. 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.

16. The Linear Variable Differential Transformer

17. 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.

18. 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.

19. 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.

20. 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.

21. Temperature Sensors

22. 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).

23. 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.

24. 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.

26. 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.

27. 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 -200oC to well over 2000oC.

28. 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.

29. The Light Sensor

31. 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).

32. 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.

33. 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 Resistor

34. The Light Dependent Resistor Cell

35. 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.

36. Photo-diode Construction and Characteristics

37. Photo-diode Amplifier Circuit

38. 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.

39. Photo-transistor Construction and Characteristics

40. 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.

41. 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 battery

42. Characteristics of a typical Photovoltaic Solar Cell.

43. The Sound sensor

44. 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.

45. 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.

46. The Microphone Transducer
The Microphone, also called a "mic", is a sound transducer that can be classed as a "sound sensor".

47. Actuators

48. 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.

49. 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.

50. Electromechanical Relay Construction

51. Relay Contact Configurations
Where:
C is the Common terminal
NO is the Normally Open contact
NC is the Normally Closed contact

52. 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.

53. 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.

54. 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.

55. Pull-type Linear Solenoid Construction

56. 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).

57. 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.

58. Most used Actuators Brushed Motor Brushless Motor Stepper motor
Servo Motor

59. 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.

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

61. SMART SENSORS

62. 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."

63. 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
Processor

64. Infrared detector array Accelerometer Integrated multisensor
Types of Smart Sensors
Optical Sensor
Infrared detector array
Accelerometer
Integrated multisensor

65. 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.

66. 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.

67. 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.

68. 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.

69. Advantages Minimum Interconnecting Cables High Reliability
High Performance
Easy to Design, Use and Maintain
Scalable -Flexible System
Small Rugged Packaging
Minimum Cost

70. 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 Networks

71. 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.

72. Sensor Application

73. Application
Level Measurement
in Large Vessels (Tanks, Silos)
Sensor
3RG61 13
Compact Range III

74. Application
anti-Collision
Sensor
3RG60 14
Compact Range I

75. Application
Level Measurement in
Small Bottles
Sensor
3RG61 12
Compact Range III

76. Application
height Sensing
Sensor
3RG60 13
Compact Range II

77. Application
Quality Control
Sensor
3RG61 12
Compact Range III

78. Application
Breakage Sensing
Sensor
3RG61 12
Compact Range I

79. Application
Bottle Counting
Sensor
3RG62 43
Thru Beam

80. Application Object Sensing Sensor 3RG60 12 Compact Range II

81. Application Vehicle Sensing and Positioning Sensor 3RG60 14 Compact Range III

82. Application Stack Height Sensing Sensor 3RG60 13 Compact Range II

83. Application Contour Recognition Sensor 3RG61 13 Compact Range III

84. Application
Diameter Sensing and
Strip Speed Control
sensor
3RG61 12
compact Range III

85. Application People Sensing Sensor 3RG60 12 Compact Range II

86. Application Wire and Rope Breakage Monitoring Sensor 3RG60 12 Compact Range I

87. Application
Loop Control
Sensor
3RG60 15
Compact Range II

88. Application Verifying Objects in Clear Bottles Sensor M12 thru Beam

89. Application Flow of Pallets Carrying Bottles Sensor 40 Retro reflective

90. Application Counting Cans Sensor K50 Polarized Retro reflective

91. Application Counting Bottles Sensor SL18 Retro reflective

92. Application Counting Cartons Sensor K65 Retro reflective

93. Application Car Wash Sensor SL Thru Beam

94. Application Reading Reference Marks for Trimming Sensor C80 Mark Sensor

95. Application Detecting Persons Sensor K50 Retro reflective

96. Application Controlling Parking Gate Sensor SL Retro reflective

97. Application End of Roll Detection Sensor K31 Diffuse

98. Application Detecting Tab Threads Sensor KL40 Fibber Optic

99. Application
Detecting Caps on Bottles
Sensor
K20 Diffuse with Background Suppression and K31 thru Beam

100. Application Counting Packages Sensor K80 Retro reflective

101. Application Detecting Components inside Metal Can Sensor K50 Background Suppression

102. Application Determining Orientation of IC Chip Sensor L50 Laser with Background Suppression

103. Application Detecting Items of Varying Heights Sensor K80 Background Suppression

104. Application Detecting Orientation of IC Chip Sensor Colour Mark or Fibber Optic

105. Application Controlling Height of a Stack Sensor SL Thru Beam

106. Application Detecting Jams on a Conveyor Sensor K50 Retro reflective

107. Application Counting Boxes Anywhere on a Conveyor Sensor SL18 Right Angle Retro reflective

108. Application Counting IC Chip Pins Sensor KL40 Fibber Optic

109. Application
Batch counting and Diverting Cans without Labels
Sensor
K40 Polarized

110. Application Detecting Presence of Object to Start a Conveyor Sensor K35 Retro reflective

111. Application Detecting Reflective Objects Sensor K80 Polarized Retro reflective

112. Application Verifying Liquid in Vials Sensor K35 Fibber Optic

113. Application Verifying Screws are Correctly Seated Sensor KL40 Fibber Optic

114. Application Verifying Cakes are Present in Transparent Package Sensor KL40 Fibber Optic

115. Application Verifying Lipstick Height before Capping Sensor M5 or M12 thru Beam

116. Application Detecting Labels with Transparent Background Sensor G20 Slot Sensor

117. Application Monitoring Objects as they Exit Vibration Bowl Sensor K35 Fibber Optic

118. Application Detecting the Presence of a Broken Drill Bit Sensor 12 mm Normal Requirements

119. Application Detecting Milk in Cartons Sensor Capacitive

120. Application Controlling Fill level of solids in a bin Sensor Capacitive

121. Application Detecting Full Open or Closed Valve Position Sensor 12mm or 18mm Extra Duty

122. Application Detecting Presence of Can and Lid Sensor 30mm Normal Requirements or UBERO, 18mm Normal Requirements Gating Sensor

123. Application Detecting Broken Bit on Milling Machine Sensor 18 mm

124. Thank you…..