chapter two: sensor and its application to students.pptx

sensor with their application

1. Chapter- two Sensors and Its Application 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 1

2. Sensors and Applications C ontents Temperature and Heat sensor Pressure sensors Level and flow sensors Biomedical applications 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 2

3. Introduction We saw that, in general, a measurement system consists of four types of element: sensing, signal conditioning, signal processing and data presentation elements. The sensing element is the first element in the measurement system; it is in contact with, and draws energy from, the process or system being measured. The input to this element is the true value of the measured variable; the output of the element depends on this value. The purpose of this chapter is to discuss the principles and characteristics of sensing elements in wide current use. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 3

4. Review of Sensors Basics Sensors : A device that receives a stimulus [ measurand ] and responds with an electrical signal . Purpose of sensor To respond to any input stimuli [ physical variable ]convert them to electrical signal compatible to electronic circuits Sensor does not function by itself in turn it is a part of the larger system that may incorporate detectors, signal conditioners, signal processors, memory devices, data recorders, actuators etc…. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 4

5. Transducer, Sensor, and Actuator 5 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. Transducer : a device that converts energy from one form to another Sensor : converts a physical parameter to an electrical output (a type of transducer, e.g. a microphone) Actuator : converts an electrical signal to a physical output (opposite of a sensor, e.g. a speaker)

6. 6 Sensor and transducer ‘Sensor' is `a device that detects a change in a physical stimulus and turns it into a signal which can be measured or recorded. E.g. : Thermistor ‘Transducer' is 'a device that transfers power from one system to another in the same or in the different form'. E.g. Thermistor with it associate circuit convert heat to electricity. As a comparison… ‘Sensor' for the sensing element itself and 'transducer' for the sensing element plus any associated circuitry. All transducers would thus contain a sensor and most (not all) sensors would also be transducers. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T.

7. Functions of transducer 7 1. To sense the presence, magnitude, change in, and frequency of some measurand . 2. To provide an electrical output that, when appropriately processed and applied to readout device, gives accurate quantitative data about the measurand Transducer Electrical output Measurand Excitation Measurand – refers to the quantity, property or condition which the transducer translates to an electrical signal. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T.

8. Type of Sensors 8 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. Displacement Sensors: resistance, inductance, capacitance, piezoelectric Temperature Sensors: Thermistors, thermocouples Electromagnetic radiation Sensors: Thermal and photon detectors

9. Classification of Transducers Transducers On The Basis of principle Used Active/Passive Primary/Secondary Analogue/Digital Capacitive Inductive Resistive Transducers/ Inverse Transducers Transducers may be classified according to their application, method of energy conversion, nature of the output signal, and so on. 9 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T.

10. Displacement Measurements Used to measure directly and indirectly the size , shape , and position of the organs. Displacement measurements can be made using sensors designed to exhibit a resistive , inductive , capacitive or piezoelectric change as a function of changes in position. 10 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T.

11. CLASSIFICATION OF PASSIVE TRANSDUCERS 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 11

12. PASSIVE TRANSDUCERS Resistive transducers : Resistive transducers are those transducers in which the resistance change due to the change in some physical phenomenon. The resistance of a metal conductor is expressed by a simple equation. R = ρ L/A Where R = resistance of conductor in Ω L = length of conductor in m A = cross sectional area of conductor in m 2 ρ = resistivity of conductor material in Ω -m. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 12

13. Types of sensors and their output 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 13

14. Temperature sensors Temperature sensor is an important parameter in many control systems. Temp. is not measure directly like displacement, pressure or flow. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 14

15. Temperature sensors Types of Temperature Sensors Resistive Temperature Detector (RTD) Thermocouple Thermistor 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 15

16. Temprature measurement The hotness or coldness of a piece of plastic, wood, metal, or other material depends upon the molecular activity of the material. Kinetic energy (KE) is a measure of the activity of the atoms which make up the molecules of any material. Therefore , temperature is a measure of the KE of the material in question. Whether you want to know the temperature of the surrounding air, the water cooling a car’s engine, or the components of a nuclear facility, you must have some means to measure the KE of the material. Most temperature measuring devices use the energy of the material or system they are monitoring to raise (or lower) the KE of the device. Instrumentation Eng| ECE_4154 | sem I | 2024 A.Y| Mr. Muluken T. 16 3/12/25

17. Temperature measurement is a crucial aspect of various industries and scientific fields, playing a pivotal role in ensuring safety, quality control, and accurate research. Temperature instruments are devices designed to measure and monitor temperatures, aiding in a wide range of applications from meteorology to manufacturing. 3/12/25 Instrumentation Eng| ECE_4154 | sem I | 2024 A.Y| Mr. Muluken T. 17 Temprature measurement

18. Understanding Temperature Instruments Temperature instruments are tools used to quantify the thermal state of an object or environment . They provide essential information about the kinetic energy of particles within a substance, indicating whether it’s hot or cold. These instruments help us make informed decisions, optimize processes, and maintain optimal conditions. They come in various forms, each suited for specific scenarios and accuracy requirements. 3/12/25 Instrumentation Eng| ECE_4154 | sem I | 2024 A.Y| Mr. Muluken T. 18

19. Measuring Units in Temperature Instruments Here are some common measuring units used in temperature instruments: Celsius (°C):   centigrade scale, is widely used in temperature instruments. It is based on the freezing and boiling points of water. On this scale, water freezes at 0°C and boils at 100°C at standard atmospheric pressure . Fahrenheit (°F):  The Fahrenheit scale is another common unit of temperature measurement, primarily used in the United States and a few other countries. On this scale, water freezes at 32°F and boils at 212°F at standard atmospheric pressure. Kelvin (K):  The Kelvin scale is an absolute temperature scale that starts from absolute zero, the point at which all thermal motion ceases. K = °C + 273.15 . 3/12/25 Instrumentation Eng| ECE_4154 | sem I | 2024 A.Y| Mr. Muluken T. 19

20. Types of Temperature Instruments Thermocouples :   This effect involves the generation of a voltage at the junction of two different metals when subjected to a temperature gradient. The voltage generated is proportional to the temperature difference. Thermocouples are rugged, and are often used in industrial settings. Thermistors:   Thermistors are temperature-sensitive resistors whose resistance changes significantly with temperature. They are highly accurate within a limited temperature range and find application in medical devices, automotive systems, and consumer electronics. 3/12/25 Instrumentation Eng| ECE_4154 | sem I | 2024 A.Y| Mr. Muluken T. 20

21. Resistance Temperature Detectors (RTDs):   Temperature sensors made of materials whose electrical resistance increases with temperature. Platinum-based RTDs are popular due to their accuracy and stability over a broad temperature range. Bimetallic Temperature Sensors:   These sensors consist of two different metal strips bonded together, each with different thermal expansion coefficients. As the temperature changes, the strips bend, which is translated into a mechanical displacement that can be measured. Bimetallic temperature sensors are commonly found in thermostats and household appliances, 3/12/25 Instrumentation Eng| ECE_4154 | sem I | 2024 A.Y| Mr. Muluken T. 21 Types of Temperature Instruments

22. Infrared Temperature Sensors:   Infrared sensors measure temperature without physical contact. They detect the infrared radiation emitted by an object and convert it into a temperature reading. Infrared thermometers are valuable in situations where non-contact measurement is necessary, such as in the food industry, medical diagnostics, and building inspections. 3/12/25 Instrumentation Eng| ECE_4154 | sem I | 2024 A.Y| Mr. Muluken T. 22 Types of Temperature Instruments

23. Working Principles The working principle of temperature instruments varies based on their type. Thermocouples , for instance, rely on the principle that two different metals will generate a voltage when exposed to different temperatures. This voltage can be translated into a temperature reading. Thermistors work by exploiting the temperature-dependent resistance of certain materials. RTDs use the fact that the electrical resistance of metals changes predictably with temperature. Infrared temperature sensors work by capturing the thermal radiation emitted by an object. All objects emit infrared radiation as a function of their temperature. The sensor detects this radiation, and by using complex algorithms and calibration, it calculates the temperature of the object without any physical contact. 3/12/25 Instrumentation Eng| ECE_4154 | sem I | 2024 A.Y| Mr. Muluken T. 23

24. Applications Healthcare :  Infrared thermometers are used for non-contact temperature measurements in medical settings, offering quick and hygienic readings. They are particularly useful for monitoring body temperature in large groups of people, as seen during disease outbreaks. Food Industry:  Temperature control is critical in food processing and storage. Instruments like thermocouples and infrared thermometers ensure food safety by monitoring temperatures during cooking, refrigeration, and transport. Manufacturing:  Industries such as metallurgy, plastics, and electronics rely on temperature instruments to maintain specific temperatures during various manufacturing processes. This ensures product quality and consistency. 3/12/25 Instrumentation Eng| ECE_4154 | sem I | 2024 A.Y| Mr. Muluken T. 24

25. Environmental Monitoring:  Weather stations use temperature instruments to record and predict weather patterns. Scientists study temperature variations in oceans, lakes, and air to understand climate change and its impacts. HVAC Systems:  Heating, ventilation, and air conditioning systems depend on temperature sensors to regulate indoor climate. Accurate temperature measurement ensures energy efficiency and occupant comfort. Automotive:  Temperature instruments play a role in engine monitoring, ensuring optimal operating temperatures. They also contribute to the functioning of air conditioning systems within vehicles . 3/12/25 Instrumentation Eng| ECE_4154 | sem I | 2024 A.Y| Mr. Muluken T. 25 Applications

26. Resistive Temperature Detector (RTD): RTDs are  sensors used to measure temperature by correlating the resistance of the RTD element with temperature used to replace any temperature sensing device provided that it meets the intent of the 3A Standards requirements. Because temperature is one of the most important parameters of a material, many instruments have been developed to measure it. One type of detector used is the RTD. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 26

27. RTD Construction and Operation of RTD RTD elements are normally constructed of platinum, copper & nickel. These metals are best suited for RTD applications because of their linear resistance-temperature characteristics (as shown in Fig. below), their high coefficient of resistance, and their ability to withstand repeated temperature cycles. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 27

28. HOW DO RTD WORK? The electrical resistance of the platinum changes as the processing temperature changes. An electronic indicator measures this resistance and the temperature and then displayed or recorded on a chart. Special sheath fillings are used when constructing these devices to ensure that they meet legal response time specifications. Platinum is the most widely used metal for RTDs due to the following characteristics: Chemical inertness . A temperature coefficient of resistance that is large enough to give readily An almost strain free fabrication metal (in that resistance doesn’t drastically change with strain). An almost linear relation between resistance and temperature. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 28

29. Resistance to Temperature relationship 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 29

30. Typical Application of RTD Food Service. Semiconducting. Packaging. Hot Melt Dispensing. Vacuum Sealing and Forming. Automotive Medical/ Laboratory Settings. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 30

31. Typical of Application It is widely used in furnaces for automatic temperature measurement. Due to its compactness, it replaces conventional thermometers as well as thermocouples thus eliminating the use of lots of wires. Used in medical and chemical laboratories to detect very low temperatures (like dry ice and liquid nitrogen). Due to electrical output it is used wherever feedback system is required and corrective action is thus taken in an automated system. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 31

32. ADVANTAGE Vs. DISADVANTAGE of RTD 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 32

33. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 33 Types of Temperature Sensors Resistive Temperature Detector (RTD) Thermocouple Thermistor

34. Thermocouple A thermocouple is another sensor for measuring temperature. Thermocouples are among the easiest temperature sensors to use and obtain and are widely used in science and industry. It is based on the principle of “ Seeback effect ”. Based on the generation of thermoelectricity. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 34

35. Basic Working Principle of Thermocouple The principle of operation is on the Seeback effect. A temperature gradient along a conductor creates an EMF. If two conductors of different materials are joined at one point , an EMF is created between the open ends which is dependent upon the temperature of the junction. As T1 increases, so does V. The EMF also depends on the temperature of the open ends T2. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 35 (  is the Seebeck coefficient for small delta T) The junction is placed in the process, the other end is in iced water at 0C. This is called the reference junction .

36. Types of thermocouple “J” Type iron and constantan “K” Type chromel and alumel . “E” Type chromel and constantan “T” Type copper and constantan 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 36

37. Practical Thermocouple Construction 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 37 Any time a pair of dissimilar wires is joined to make a circuit and a thermal gradient is imposed, an emf voltage will be generated. Twisted, soldered or welded junctions are acceptable. Welding is most common. Keep weld bead or solder bead diameter within 10-15% of wire diameter Welding is generally quicker than soldering but both are equally acceptable Voltage or EMF produced depends on: Types of materials used Temperature difference between the measuring junction and the reference junction

38. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 38

39. Comparison of Temperature sensors 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 39

40. Application of Thermocouple 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 40

41. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 41 Types of Temperature Sensors Resistive Temperature Detector (RTD) Thermocouple Thermistor

42. Thermistor A therm istor is a combination of two word thermal and resistor . A thermistor is a types of resistor used to measure temperature changes, relying on the change in its resistance with changing temperature. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 42

43. Thermistor A semiconductor used as a temperature sensor. Mixture of metal oxides pressed into a bead, wafer or other shape . Beads can be very small, less than 1mm in some cases. The resistance decreases as temperature increases , negative temperature coefficient (NTC) thermistor. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 43

44. Negative temperature coefficient Thermistor resistance Vs Temperature relationship (NTC) A non linear decrease in resistance as temperature increase. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 44

45. Advantage Vs Disadvantage of Thermistors 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 45

46. Applications of Thermistor Temperature measurement Time delay (self heating from large current ’opens’ the thermistor so it can be used as a slow switch). Surge suppression where R resistance and I is the current needs to flow through the thermistor for awhile to heat it so that it ‘opens’, and acts again as a switch. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 46

47. Resistance Vs Temperature 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 47

48. Pressure Sensors A pressure sensor measures pressure, typically of gases or liquids. Pressure is an expression of the force required to stop a fluid from expanding, and is usually stated in terms of force per unit area . A pressure sensor usually acts as a transducer; it generates a signal as a function of the pressure imposed. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 48

49. Pressure Sensors Types of Pressure Sensors Bellows-Type Detectors Bourdon Tube-Type Detectors Strain gauge type pressure transducer Capacitive type pressure transducer 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 49

50. Bellows-Type Detectors Do you know how we can measure the pressure of flow of water in a peaceful river? Actually there are many instruments by which we can measure the pressure of flow. One of the instrument that can use the measure the pressure of flow is bellows pressure gauge. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 50

51. Working principle of bellow pressure gauge As we start the water supply in the pipeline the water strikes the tubular membranes known as bellow . Then the pressure to be measured is applied outside the bellow. A bellow gauge contains an elastic element ( i.e spring) that is a convoluted unit that expands and contracts axially with changes in pressure . 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 51

52. Constraction of bellow chamber The spring in bellows gauges is made of; brass phosphor bronze, stainless steel or other metal that is suitable for the intended purpose of the gauge 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 52

53. The movement of the bellows can be converted into linear displacement, This displacement can be converted in term of pressure As flow of pressure increases , a pointer starts rotating on the dial which indicates the pressure of the flow and to make this measurement precise the scale of the dial is divided in many sectors. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 53

54. After some time the pointer assumes a new position calibrated scale on the dial to indicate the applied pressure directly. And thus pressure is measured on the dial . 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 54

55. Hardware diagram of bellow type 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 55

56. Types of Pressure Sensors Bellows-Type Detectors Bourdon Tube-Type Detectors Strain gauge type pressure transducer Capacitive type pressure transducer 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 56

57. Bourdon Tube-Type Detectors Bourdon tube pressure gauge are used for the pressure measurement of relative pressure from 0.6 bar to 7,000 bars. They are classified as mechanical pressure measuring instrument and thus operate without any electrical power . 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 57

58. Working principle When an elastic transducer such as bourdon tube in this case is subjected to a pressure it deflects This deflection is proportional to the applied pressure when calibrated. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 58

59. Working principle As the fluid pressure enters the bourdon tube, it tries to be reformed and because of a free tip available, this action causes the tip to travel in free space and the tube unwinds. The simultaneous actions of bending and tension due to the internal pressure make a non-linear movement of the free tip. This travel is suitable guided and amplified for the measurement of the internal pressure. But the main requirement of the device is that whenever the same pressure is applied, the movement of the tip should be the same and on withdrawal of the pressure the tip should return to the initial point. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 59

60. Cont… A lot of compound stresses originate in the tube as soon as the pressure is applied. This makes the travel of the tip to be non-linear in nature. If the tip travel is considerably small, the stresses can be considered to produce a linear motion that is parallel to the axis of the link. The small linear tip movement is matched with a rotational pointer movement. This is known as multiplication, which can be adjusted by adjusting the length of the lever. For the same amount of tip travel, a shorter lever gives larger rotation. The approximately linear motion of the tip when converted to a circular motion with the link-lever and pinion attachment, a one-to-one correspondence between them may not occur and distortion results. This is known as angularity which can be minimized by adjusting the length of the link. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 60

61. Construction A ‘C’ type burden tube consists of a long thin walled cylinder have non circular cross-section which is sealed at one end. This tube is made from materials such as phosphor bronze, steel and beryllium copper.. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 61

62. And attached by a light mechanism which operates the pointer. The other end of the tube is fixed and is open for the application of the pressure which is tube measured 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 62

63. C-type, bourdon gauges can also be constructed in the form of a helix or a spiral. The types are varied for specific uses and space accommodations, for better linearity and larger sensitivity. For thorough repeatability, the bourdon tubes materials must have good elastic or spring characteristics. The surrounding in which the process is carried out is also important as corrosive atmosphere or fluid would require a material which is corrosion proof. The commonly used materials are phosphor-bronze, silicon-bronze, beryllium-copper, inconel, and other C-Cr-Ni-Mo alloys, and so on. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 63

64. Internal curcuit diagram of bourdon tube 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 64

65. Advantage Those burden tube pressure gauge give accurate results. The cost of bourdon tube pressure gauge is low Burden tube are simple in construction They can be modified to give electrical output. They are safe even for high pressure measurement Accuracy is high especially at high pressures. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 65

66. Disadvantage They response slowly to changes in pressure. They are subjected to hysteresis. They are sensitive to shocks and vibrations. Amplifications is a must as the displacement of the free end of the bourdon tube is low. It can’t be used for precision measurement. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 66

67. Types of Pressure Sensors Bellows-Type Detectors Bourdon Tube-Type Detectors Strain gauge type pressure transducer Capacitive type pressure transducer 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 67

68. Strain gauge type pressure transducer Strain gauge type pressure transducer is a passive transducer that converts a mechanical displacement into a change of resistance . Resistance changes as both length and diameter of the conductor changes . 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 68

69. What is strain gauge? It is a thin, wafer-like device that can be attached to a variety of materials by a suitable adhesive to measure the applied strain. As the structure is stressed, the resulting strain deforms the strain gauge attached to the structure. It causes an increase in the resistivity of the gauge which produces an electrical signal proportional to the deformation. The strain gauge displacement sensor consists of a structure attached with the strain gauge that elastically deforms when subjected to a displacement 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 69

70. Working principle 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 70

71. When force is applied to any metallic wire its length increases due to the strain. If L1 is the initial length of the wire and L2 is the final length after application of the force, the strain is given as : 𝜖= Further, as the length of the stretched wire increases, its diameter decreases. so that resistance of the conductor is the direct function of the length. As the length of the conductor increases its resistance increases. This change in resistance of the conductor can be measured easily and calibrated against the applied force. Thus strain gauges can be used to measure force and related parameters like displacement and stress. The input and output relationship of the strain gauges can be expressed by the term gauge factor or gauge gradient, which is defined as the change in resistance R for the given value of applied strain ε.   12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 71

72. strain gauge with Wheatstone bridge The change of resistance is very small and it is usually measured using a Wheatstone bridge circuit where a strain gauge is connected into the circuit with a combination of four active gauges for full-bridge, two gauges for half-bridge or a single gauge for the quarter bridge. In half and quarter circuits, the bridge is completed with precision resistors. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 72

73. Advantages of Strain Gauge ( i) There is no moving part and hence no wear (ii) Strain gauges are very precise (iii) It is small and inexpensive (iv) It has a high-frequency bandwidth. Disadvantages of Strain Gauge ( i) It is non-linear (ii) It is very sensitive to temperature. (iii) It needs to be calibrated regularly (iv) Strain gauges have to be applied manually. Putting them in their place consuming and costly. It is one of their biggest disadvantages 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 73

74. Types of Pressure Sensors Bellows-Type Detectors Bourdon Tube-Type Detectors Strain gauge type pressure transducer Capacitive type pressure transducer 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 74

75. Capacitive type pressure transducer Capacitive pressure sensors are devices that measure pressure changes by detecting the variation in capacitance caused by the movement of a diaphragm, which is the ability of a system to store an electric charge. Capacitive pressure sensors are widely used in various applications, including automotive, aerospace, medical, and industrial sectors, due to their high sensitivity, low power consumption, and excellent long-term stability. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 75

76. Capacitive type pressure transducer 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 76

77. Working Principle Capacitive pressure sensors are based on the principle that the capacitance between two parallel plates is inversely proportional to their separation distance. When pressure is applied to a flexible diaphragm, one of the plates, it causes the diaphragm to deflect, altering the distance between the two plates and consequently changing the capacitance value. This change in capacitance can be measured and calibrated to represent the pressure exerted on the sensor. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 77

78. Advantage High sensitivity, allowing for the detection of small pressure changes Low power consumption, making them suitable for battery-powered applications Excellent long-term stability and low hysteresis Minimal temperature dependence, enabling reliable performance over a wide temperature range 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 78

79. Disadvantage T hey can be susceptible to external electromagnetic interference, which may affect the accuracy of the sensor readings. Additionally , capacitive sensors typically require more complex signal conditioning circuitry compared to other pressure sensing technologies, which can increase the overall cost and complexity of the system. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 79

80. Level Sensor Level sensors can be categorised as either contact or non-contact, depending on the specific type. The methods used to determine fluid levels are explored below by type – here is a handy overview : Optical Level Sensors  – visible, laser, or infrared light Capacitive Level Sensors  – non-contact sensing fields Conductive Level Sensors  – electrical contact outputs Vibrating Level Sensors  – high-frequency vibrations Ultrasonic Level Sensors  – ultrasonic pulses Microwave Level Sensors  – electromagnetic energy 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 80

81. Requirement to use level sensor These factors include: What substance will be measured Where the sensor will be used What position the sensor needs to be mounted in 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 81

82. Level Sensors Types of Level Sensors Gauge Glass Type Level Detector Ball Float Type Level Detector Chain Float Type Level Detector Magnetic Bond Method Level Detector Conductive Probe Method Level Detector 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 82

83. Gauge Glass Type Level Detector It consist of a transient level gauge employ transparent glass fitted with a liquid chamber/ tank on one side or either sides of the tank. The gauge glass is marked with graduations to allow the level to be measured It consists of two isolation values which can be used during maintenance 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 83

84. Level gauge Level gauge  is a device which is used to show the level of fluids in fields. Depending on the type of application used, the type of level gauge should be selected. Level gauge is a direct method for measuring the level . Level gauge consists of a metal body, machined to have an internal chamber and one or more front windows. On each window a special high resistance glass is used with sealing joint and metal cover plate hold by bolts and nuts . Level devices operate under three main different principles: The position (height) of the liquid surface The pressure head  The weight of the material 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 84

85. Working principle Gauge glass is probably the simplest method of measuring liquid level. The gauge glass is attached to the outside of the tank so that the liquid level can be seen through the glass . The liquid level is indicated as a result of difference in the transparent properties of the two media. A d rain is provided at the bottom of gauge as shown in figure . For water/steam applications, an illuminator is mounted on the rear side of the gauge with its light rays deflected upward into the water column. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 85

86. Types of level gauges 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 86

87. Types of Level Sensors Gauge Glass Type Level Detector Ball Float Type Level Detector Chain Float Type Level Detector Magnetic Bond Method Level Detector Conductive Probe Method Level Detector 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 87

88. Ball Float Type Level Detector The float is made of current resistive material which floats on the surface of the liquid. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 88

89. The change in the level of the liquid is noted on the float. As the level of the water in the tank varies, the float is also raised or lower Depending on the position of the float , the pulley rotates and the pointer moves over the graduated scale. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 89

90. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 90

91. Types of Level Sensors Gauge Glass Type Level Detector Ball Float Type Level Detector Chain Float Type Level Detector Magnetic Bond Method Level Detector Conductive Probe Method Level Detector 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 91

92. Chain Float Type Level Detector This type of float gauge has a float ranging in size up to 12 inches in diameter and is use where small level limitations imposed by ball floats must be exceeded. The range of level measured will be limited only by the size of the vessel. The operation of the chain float is similar to the ball float except in the method of positioning the pointer and in its connection to the position indication . 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 92

93. Chain Float Type Level Detector The float is connected to a rotating element by a chain with a weight attached to the other end to provide a means of keeping the chain taut during changes in level. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 93

94. Comparison Ball float type level detector Chain float type level detector 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 94

95. Types of Level Sensors Gauge Glass Type Level Detector Ball Float Type Level Detector Chain Float Type Level Detector Magnetic Bond Method Level Detector Conductive Probe Method Level Detector 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 95

96. Magnetic Bond Method Level Detector The magnetic bond method was developed to overcome the problems of cages and stuffing boxes. The magnetic bond mechanism consists of a magnetic float which rises and falls with changes in level. The float travels outside of a non-magnetic tube which houses an inner magnet connected to a level indicator. When the float rises and falls, the outer magnet will attract the inner magnet, causing the inner magnet to follow the level within the vessel 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 96

97. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 97 Fig: Magnetic Bond level detector.

98. Magnetic Bond Method Level Detector The magnetic level indicator working principle is widely used in level instrumentation. The interaction between float magnets inside the chamber and magnetic flags outside the chamber provide virtually maintenance-free, continuous level information. This type of level indicator doesn’t require power, making it ideal for a variety of applications across industries . The magnetic level indicator working principle is based on the effects that one magnet has on nearby magnets. The mechanics are simple yet very effective, yielding reliable and repeatable level information for continuous monitoring and recording of fluid levels. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 98

99. Working principle The level indicator is attached to the vessel and connects directly with the fluid to be measured. Within the chamber is a float with a magnet assembly inside. This float rests on the fluid’s surface. As the fluid level rises or falls, so does the float. As the float moves up or down, the magnet assembly rotates a series of bi-color magnetic flags or flaps, changing the visual indicators mounted just outside the chamber from one color to the other.   12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 99

100. Advantages An additional advantage: The indicator’s magnetic force can affect optional switches or transmitters mounted outside of the chamber. The colored flags are easy to see, even from a distance, and are paired with a scale for precise readings. As for any level instrumentation, the size and material of the float are chosen according to the media, temperature, pressure, and density of the process media. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 100

101. Types of Level Sensors Gauge Glass Type Level Detector Ball Float Type Level Detector Chain Float Type Level Detector Magnetic Bond Method Level Detector Conductive Probe Method Level Detector 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 101

102. Conductive Probe Method Level Detector It consists of one or more level detectors, an operating relay, and a controller. When the liquid makes contact with any of the electrodes, an electric current will flow between the electrode and ground. The current energizes a relay which causes the relay contacts to open or close depending on the state of the process involved. The relay in turn will actuate an alarm, a pump, a control valve, or all three. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 102

103. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 103 A typical system has three probes: a low level probe , a high level probe , and a high level alarm probe.

104. Advantage and disadvantage The advantage of using conductive probes are their low cost and simple to design. The disadvantage of using conductive probes are the fact that they are limited to point measurements and can only be with conductive liquids 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 104

105. Applications of Level Sensors Fuel Level Sensor in Generator, Car, etc : Water Level Sensor in Boilers: Water Level Control in Elevated Tanker: E.t.c . 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 105

106. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 106

107. Individual Assignment (10%) Flow sensor position sensor Your document Include those thing: Definition Type Working principle Advantage and disadvantage Application area With Hand writing document physical submission and also softcopy send to email address. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 107

108. 12 March 2025 ECEg 4119 | Ch–2 | Year IV/ Sem I | 2025 Ac. Year | ECE | Muluken T. 108