1. SNJB’s LATE SAU. K.B. JAINCOLLEGE OF ENGINEERINGNEMINAGAR, CHANDWADNAAC ACCREDITED WITH “A” GRADE Course: Sensors in Automation (304195B) Unit 1- Introduction to Sensors & Transducers AI & DS | CIVIL | COMP | E&TC | MECH | MBA

2. Contents • Concept of Sensor • Concept of Transducer • Comparison between Sensors and Transducers • Role of Sensors in Automation • Broad Classification of Sensors and Transducers • Role of Transducer in measurement Systems • Block Diagram of Measurement system SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

3. Contents • Study of Static and Dynamic Characteristics of Measurement Systems: Accuracy, Precision, Reproducibility, Linearity, repeatability, resolution, Sensitivity, Range, Span, Dead Zone, Hysteresis, Backlash, Dynamic Characteristics: Fidelity, Time response and frequency response, Classification of errors – Error analysis. • Concept and Basic Principle of working of Resistive Capacitive and Inductive sensors. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

4. Concept of Sensor • A sensor is a device that detects and responds to some type of input from the physical environment. The specific input could be light, heat, motion, moisture, pressure, or any one of a great number of other environmental phenomena. The output is generally a signal that is converted to human-readable display at the sensor location or transmitted electronically over a network for reading or further processing. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

5. Concept of Sensor • Here are a few examples of the many different types of sensors: • In a mercury-based glass thermometer, the input is temperature. The liquid contained expands and contracts in response, causing the level to be higher or lower on the marked gauge, which is human-readable. • An oxygen sensor in a car's emission control system detects the gasoline/oxygen ratio, usually through a chemical reaction that generates a voltage. A computer in the engine reads the voltage and, if the mixture is not optimal, readjusts the balance. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

6. Concept of Sensor • Motion sensors in various systems including home security lights, automatic doors and bathroom fixtures typically send out some type of energy, such as microwaves, ultrasonic waves or light beams and detect when the flow of energy is interrupted by something entering its path. • A photo sensor detects the presence of visible light, infrared transmission (IR), and/or ultraviolet (UV) energy. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

7. Concept of Transducer • A device which converts a physical quantity into the proportional electrical signal is called a transducer. The electrical signal produced may be a voltage, current or frequency. A transducer uses many effects to produce such conversion. The process of transforming signal from one form to other is called transduction. A transducer is also called pick up. The transduction element transforms the output of the sensor to an electrical output, as shown in the Fig. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

8. Concept of Transducer Sensor Response Sensing Element Transduction Element Non- Electrical Quantity Electrical Quantity • A transducer will have basically two main components. They are • 1. Sensing Element: The physical quantity or its rate of change is sensed and responded to by this part of the transistor. • 2. Transduction Element The output of the sensing element is passed on to the transduction element. This element is responsible for converting the non-electrical signal into its proportional electrical signal. • There may be cases when the transduction element performs the action of both transduction and sensing. The best example of such a transducer is a thermocouple. A thermocouple is used to generate a voltage corresponding to the heat that is generated at the junction of two dissimilar metals. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

9. Comparison between Sensors & Transducer SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

10. Comparison between Sensors & Transducer SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

11. Role of Sensors in Automation Sensors used in automation • The industry 4.0 revolution has been through a lot of technical progress. It has seen many sensing technologies in the past. But the current technology can accurately respond to the needs of the modern manufacturing process. • It has increased the production capacity with wireless and cloud-based connectivity. It has made possible the use of robotics and new IIoT devices across smart manufacturing facilities. • There are a vast number of automation sensors being used such as tilt sensing, warehouse inventory management to vibration sensing and analysis of moving parts, and thermal detection SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

12. Role of Sensors in Automation • Although there are numerous sensors used today still there are some more often and useful. The below-mentioned automation sensors are some of the most common. • Presence Detection Sensors • Photo-optical Sensors • Monitoring Sensors • Proximity measuring sensors • Data Sensors SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

13. Broad Classification of Sensors and Transducers Several criteria are adopted for the classification of sensors. Some of these include • Based on the principle of operation (transduction principle) • Based on energy requirements • Based on material and technology used • Application-based classification • Property-based classification SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

14. Broad Classification of Sensors and Transducers Based on transduction principles • The transduction principle is the basic criteria that should be followed for a systematic approach to classification. • This classification is based on the method used in the process of converting measurand into usable output. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

15. Broad Classification of Sensors and Transducers Active/Passive Transducers • Based on the energy requirements of a transducer, they are classified as active transducers and passive transducers. • Active transducers do not need any external power supply to operate and hence it is also called self-generating transducers. • Eg: Thermocouple • Transducers that require an external power source to operate is called Passive transducers. • Eg: LVDT SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

16. Broad Classification of Sensors and Transducers Based on material and technology Another classification is based on the material and technology that have acquired more importance lately. The following table shows the emerging sensor technologies with its applications. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

17. Broad Classification of Sensors and Transducers Application based classification Application based classification of sensors are represented as SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

18. Broad Classification of Sensors and Transducers Property based classification • A much more elaborate classification is based on the properties like pressure, displacement, temperature …etc. • It is subdivided in technology scale. Pressure property is used in technologies such as manometer and piezoelectricity. • Semiconductors and thermal conductance use gas and chemical properties SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

19. Broad Classification of Sensors and Transducers SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

20. Something OFF the Topic SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

21. Something OFF the Topic SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

22. Measurement Systems • System of measurement refers to the process of associating numbers with physical quantities and phenomena. • It is more like a collection of units of measurement and rules relating them to each other. The whole world revolves around measuring things! Everything is measured: the milk you buy, the gas you fill for the vehicle, the steps you walk. • Even our productivity is measured in terms of productivity indexes on how productively we work. System of measurement is very important and define and express the different quantities of length, area, volume, weight, in our day-to-day communications. • The system of measurement is based on two important foundation pillars of defining the basic unit of measurement, and the measure of conversion from the basic unit to other related units. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

23. Measurement Systems SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

24. Measurement Systems • In the old days, we used body parts for informal measurement systems like foot length, cubit, handspan, etc. which were not so accurate and vary from person to person. • So, there was a need to regularize the measurements. A system of measurement like the International System of Units called the SI units ( the modern form of the metric system), Imperial system, and US customary units were standardized across the world. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

25. Measurement Systems • This term measurement system includes all components in a chain of hardware and software that leads from the measured variable to processed data. • In a modern automobile there are as many as 40 – 50 sensors (measuring devices) used in implementing various functions necessary to the operation of the car. • Knowledge of the instruments available for various measurements, how they operate, and how they interface with other parts of the system is essential for every engineer. • Modern engineering systems rely heavily on a multitude of sensors for monitoring and control to achieve optimum operation. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

26. Types of Applications of Measurement Instrumentation • Every application of measurement, including those not yet invented, can be put into one of these three categories or some combination of them: – Monitoring of processes and operations – Control of processes and operations – Experimental engineering analysis SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

27. Types of Applications of Measurement Instrumentation Monitoring of Processes and Operations • Here the measuring device is being used to keep track of some quantity • Certain applications of measuring instruments may be characterized as having essentially a monitoring function • e.g., thermometers, barometers, and water, gas, and electric meters, automotive speedometer and fuel gage, and compass. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

28. Types of Applications of Measurement Instrumentation Control of Processes and Operations • One of the most important classes of measurement application. • Sensors are used in feedback-control systems and many measurement systems themselves use feedback principles in their operation. • Sensors are used in feedback systems and feedback systems are used in sensors. So an instrument can serve as a component of a control system. • To control any variable in a feedback control system, it is first necessary to measure it. Every feedback-control system will have at least one measuring device as a vital component. • A single control system may require information from many measuring instruments, e.g., industrial machine and process controllers, aircraft control systems, automotive control systems (speed control, antilock braking, coolant temperature regulating, air conditioning, engine pollution, etc.). SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

29. Feedback Control System SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

30. Types of Applications of Measurement Instrumentation Experimental Engineering Analysis • In solving engineering problems, two general methods are available: theoretical and experimental. Many problems require the application of both methods and theory and experiment should be thought of as complimenting each other. Features of Theoretical Methods • Often gives results that are of general use rather than for restricted application. • Invariably require the application of simplifying assumptions. The theoretically predicted behavior is always different from the real behavior, as a simplified physical/mathematical model is studied rather than the actual physical system. • In some cases, may lead to complicated mathematical problems. • Require only pencil, paper, computers, etc. Extensive laboratory facilities are not required. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

31. Block Diagram of Measurement System Measured Medium Primary Sensing Element Variable Conversion Element Variable Manipulation Element Data Storage / Playback Element Data Transmission Element Data Presentation Element Observer • Note: These elements are functional, not physical. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

32. Block Diagram of Measurement System Primary Sensing Element • This is the element that first receives energy from the measured medium and produces an output depending in some way on the measured quantity (measurand). The output is some physical variable, e.g., displacement or voltage. • An instrument always extracts some energy from the measured medium. The measured quantity is always disturbed by the act of measurement, which makes a perfect measurement theoretically impossible. Good instruments are designed to minimize this loading effect. Variable-Conversion Element • It may be necessary to convert the output signal of the primary sensing element to another more suitable variable while preserving the information content of the original signal. This element performs this function. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

33. Block Diagram of Measurement System Variable-Manipulation Element • An instrument may require that a signal represented by some physical variable be manipulated in some way. By manipulation we mean specifically a change in numerical value according to some definite rule but a preservation of the physical nature of the variable. This element performs such a function. Data-Transmission Element • When functional elements of an instrument are actually physically separated, it becomes necessary to transmit the data from one to another. This element performs this function. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

34. Block Diagram of Measurement System Data-Presentation Element • If the information about the measured quantity is to be communicated to a human being for monitoring, control, or analysis purposes, it must be put into a form recognizable by one of the human senses. • This element performs this “translation” function. Data Storage/Playback Element • Some applications require a distinct data storage/playback which can easily recreate the stored data upon command SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

35. Something OFF the Topic SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

36. Contents • Study of Static and Dynamic Characteristics of Measurement Systems: Accuracy, Precision, Reproducibility, Linearity, repeatability, resolution, Sensitivity, Range, Span, Dead Zone, Hysteresis, Backlash, Dynamic Characteristics: Fidelity, Time response and frequency response, Classification of errors – Error analysis. • Concept and Basic Principle of working of Resistive Capacitive and Inductive sensors. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

37. Static Characteristics of Measurement Systems 1. Accuracy: • Accuracy is the closeness with which an instrument reading approaches the true value of the quantity being measured. • Thus accuracy of a measurement means conformity to truth. The accuracy of an instrument may be expressed in many ways. • The accuracy may be expressed as point accuracy, percent of true value or percent of scale range. • Point accuracy is stated for one or more points in the range, for example, the scale of length may be read with in 0.2 mm. • Another common way is to specify that the instrument is accurate to within x percent of instrument span at all points on the scale. • Another way of expressing accuracy is based upon instrument range SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

38. Static Characteristics of Measurement Systems 2. Precision: • Precision is the degree of exactness for which the instrument is designed. • It composed of two characteristics: conformity and significant figures. • More significant figures, estimated precision is more. For example two resistors for values of 1792 ohms and 1710 ohms. A person even repeated measurement it indicates 1.7 K ohms. The reader can not read the true value from the scale. • He estimates from the scale reading consistently yield a value of 1.5 M ohms. This is as close to the true scale as he can read the scale by estimation although there are no deviations from the observed value, the error created by the limitation of the error is called precision error. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

39. Static Characteristics of Measurement Systems 3. Reproducibility & Repeatability: • Repeatability is the degree of closeness with which a given value may be repeatedly measured. • It is the closeness of output readings when the same input is applied repetitively over a short period of time. • The measurement is made on the same instrument, at the same location, by the same observer and under the same measurement conditions. It may be specified in terms of units for a given period of time. • Reproducibility relates to the closeness of output readings for the same input when there are changes in the method of measurement, observer, measuring instrument location, conditions of use and time of measurement. • Perfect reproducibility means that the instrument has no drift. Drift means that with a given input the measured values vary with time. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

40. Static Characteristics of Measurement Systems 4. Linearity: • When the input-output points of the instrument are plotted on the calibration curve and resulting curve may not be linear. • This would be only if the output is proportional to input. Linearity is the measure of maximum deviation of these points from the straight line (Fig.). • The departure from the straight line relationship is non-linearity, but it is expressed as linearity of the instrument. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

41. Static Characteristics of Measurement Systems 4. Linearity: • Linearity is expressed in many different ways: i) Independent Linearity: It is the maximum deviation from the straight line so placed as to minimize the maximum deviation (Fig.). ii) Zero based linearity: It is the maximum deviation from the straight line joining the origin and so placed as to minimize the maximum deviation. iii) Terminal based linearity: It is the maximum deviation from the straight line joining both the end points of the curve. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

42. Static Characteristics of Measurement Systems 5. Resolution: • It is the smallest quantity being measured which can be detected with certainty by an instrument. • If a non zero input quantity is slowly increased, the output reading won’t increase until some minimum change in the input takes place. The minimum change which causes the change in output is termed resolution. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

43. Static Characteristics of Measurement Systems 6. Sensitivity: • Sensitivity can also be derived as for the smallest changes in the measured variable for which the instrument responds. • Sensitivity can be defined as the ratio of a change in output to change in input which causes it, in steady-state conditions. • The usage of this term is generally limited to linear devices, where the plot of output to input magnitude is straight. • Sensitivity = Change in output / Change in input • Sensitivity can also be derived as for smallest changes in the measured variable instrument responds. • The term sensitivity is some times used to describe the maximum change in an input signal that will not initiate on the output. • Note: The sensitivity of the instrument should be high. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

44. Static Characteristics of Measurement Systems 7. Range & Span • In an analogue indicating instrument, the measured value of a variable is indicated on a scale by a pointer. • The choice of proper range of instruments is important in measurement. The region between the limits within which an instrument is designed to operate for measuring, indicating or recording a physical quantity is called the range of the instruments. • The Scale Range of an instrument is thus defined as the difference between the largest and the smallest reading of the instrument. Supposing the highest point of calibration is Xmax units while the lowest is Xmin units and the calibration is continuous between the two points, then the instrument range is between Xmin and Xmax . • Many times it is also said that the instrument range is Xmax. The instrument span is the difference between highest and the lowest point of calibration. Thus Span = Xmax - Xmin SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

45. Static Characteristics of Measurement Systems 8. Dead Zone Dead Zone: for the largest range of values of a measured variable, to which the instrument does not respond. • The dead zone occurs more often due to static friction in indicating an instrument. • A practical example is: Due to static friction, a Control valve does not open even for a large opening signals from the controller. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

46. Static Characteristics of Measurement Systems 9. Hysteresis • Hysteresis: Hysteresis: Hysteresis is a phenomenon that illustrates the different output effects when loading and unloading. • Many times, for the increasing values of input an instrument, may indicate one set of output values. For the decreasing values of the input, the same instrument may indicate its different set of output values. When output values are plotted against input the following kind of graph is obtained. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

47. Dynamic Characteristics of Measurement Systems • Fidelity • Fidelity of a system is defined as the ability of the system to reproduce the output in the same form as the input. • It is the degree to which a measurement system indicates changes in the measured quantity without any dynamic error. • Supposing if a linearly varying quantity is applied to a system and if the output is also a linearly varying quantity the system is said to have 100 percent fidelity. • Ideally a system should have 100 percent fidelity and the output should appear in the same form as that of input and there is no distortion produced in the signal by the system. • In the definition of fidelity any time lag or phase difference between output and input is not included. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

48. Dynamic Characteristics of Measurement Systems 2. Time Response & Frequency Response • Speed(Freq.) of Response is defined as the rapidity with which an instrument or measurement system responds to changes in measured quantity. • Response Time is the time required by instrument or system to settle to its final steady position after the application of the input. • For a step input function, the response time may be defined as the time taken by the instrument to settle to a specified percentage of the quantity being measured, after the application of the input. • This percentage may be 90 to 99 percent depending upon the instrument. For portable instruments it is the time taken by the pointer to come to rest within +-0.3 percent of final scale length and for switch board (panel) type of instruments it is the time taken by the pointer to come to rest within 1 percent of its final scale length. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

49. Dynamic Characteristics of Measurement Systems 3. Dynamic Error • The dynamic error is the difference between the true value of the quantity changing with time and the value indicated by the instrument if no static error is assumed. • However, the total dynamic error of the instrument is the combination of its fidelity and the time lag or phase difference between input and output of the system. • Overshoot- Moving parts of instruments have mass and thus possess inertia. When an input is applied to instruments, the pointer does not immediately come to rest at its steady state (or final deflected) position but goes beyond it or in other words overshoots its steady position. The overshoot is evaluated as the maximum amount by which moving system moves beyond the steady state position. In many instruments, especially galvanometers it is desirable to have a little overshoot but an excessive overshoot is undesirable. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR

50. Dynamic Characteristics of Measurement Systems 3. Dynamic Error • Fidelity: It is defined as the degree to which a measuring instrument is capable of faithfully reproducing the changes in input, without any dynamic error. • Lag: Every system takes at least some time to respond, whatever time it may be to the changes in the measured variable. • For Example Lag occurs in temperature measurement by temperature sensors such as Thermocouple or RTD or dial thermometer due to scale formation on thermowell due to process liquid. • Retardation lag: the response of the measurement begins immediately after the change in measured quantity has occurred. • Time delay lag: in this case after the application of input, the response of the measurement system begins with some dead times. SNJB’s LATE SAU. K. B. JAIN COLLEGE OF ENGINEERING | DEPT OF E&TC | PROF. D. J. PAWAR