ECE Elective 1 (2425 Term 1) Sensor Technology PDF

ECE Elective 1 (2425_Term 1) BETELXT-NS-T-3A-T Instrumentation (2425_Term 1) BETELXT-NS-T-3A-T  TEMPERATURE AND HEAT Instrumentati on  THERMODYNAM ICS Instrumentati on  HEAT Instrumentati on  HEAT...

ECE Elective 1 (2425_Term 1) BETELXT-NS-T-3A-T Instrumentation (2425_Term 1) BETELXT-NS-T-3A-T  TEMPERATURE AND HEAT Instrumentati on  THERMODYNAM ICS Instrumentati on  HEAT Instrumentati on  HEAT describes the transfer of thermal energy between molecules within a system and is measured in Joules. Instrumentati on  HEAT describes the transfer of thermal energy between molecules within a system and is measured in Joules. Instrumentati on  HEAT describes the transfer of thermal energy between molecules within a system and is measured in Joules. Instrumentati on  TEMPERATURE Instrumentati on  describes the average kinetic TEMPERATURE energy of molecules within a material or system and is measured in Celsius (°C), Kelvin(K), Fahrenheit (°F), or Rankine (R). Instrumentati on  describes the average kinetic TEMPERATURE energy of molecules within a material or system and is measured in Celsius (°C), Kelvin(K), Fahrenheit (°F), or Rankine (R). Instrumentati on Instrumentati on Instrumentati on  Kelvin Instrumentati on  25°C Instrumentati on  25°C To Fahrenheit Instrumentati on  25°C To Kelvin Instrumentati on  25°C To Rankine Instrumentati on  274.15K To Rankine Instrumentati on  274.15K To Fahrenheit Instrumentati on  274.15K To Celsius Instrumentati on  HEAT Instrumentati on  HEAT Methods of Heat Transfer Instrumentati on  Methods of Heat Transfer CONDUCTION occurs between objects that are touching each other. Collisions between small particles allow fast moving, or vibrating, particles to give some of their microscopic kinetic energy to slower particles. Instrumentati on  Methods of Heat Transfer CONDUCTION occurs between objects that are touching each other. Collisions between small particles allow fast moving, or vibrating, particles to give some of their microscopic kinetic energy to slower particles. Instrumentati on  Methods of Heat Transfer CONVECTION is heat transfer caused by moving fluids. In a fluid, particles can mix together, move faster, and spread out, thus distributing their thermal energy. Warm air coming from a heating vent to flow around a cool room is an example of convection. Instrumentati on  Methods of Heat Transfer CONVECTION is heat transfer caused by moving fluids. In a fluid, particles can mix together, move faster, and spread out, thus distributing their thermal energy. Warm air coming from a heating vent to flow around a cool room is an example of convection. Instrumentati on  occursMethods of the without Heatmovement Transfer of RADIATION matter. Thermal radiation is made of electromagnetic waves given off by moving particles. These waves can also be absorbed by materials. Microwave ovens work by radiation and the entire surface of the Earth is heated by the sun's Instrumentati on  occursMethods of the without Heatmovement Transfer of RADIATION matter. Thermal radiation is made of electromagnetic waves given off by moving particles. These waves can also be absorbed by materials. Microwave ovens work by radiation and the entire surface of the Earth is heated by the sun's Instrumentati on  TEMPERATURE SENSORS Instrumentati on  detect a change in TEMPERATURE a physical SENSORS parameter such as resistance or output voltage that corresponds to a temperature change. Instrumentati on  2 BASIC TYPES OF TEMPERATURE SENSING Instrumentati on  2 BASIC TYPES OF TEMPERATURE SENSING 1.Contact 2.Non-contact Instrumentati on  temperature sensing CONTACT requires the sensor to be in direct physical contact with the media or object being sensed. It can be used to monitor the temperature of solids, liquids or gases over an extremely wide temperature range. Instrumentati on  measurement interprets the radiant NON-CONTACT energy of a heat source in the form of energy emitted in the infrared portion of the electromagnetic spectrum. This method can be used to monitor non- reflective solids and liquids but is not effective with gases due to their natural transparency. Instrumentati on  TEMPERATURE SENSORS FAMILY Temperature Sensors Electro- Electronic Resistive Mechanical Instrumentati on  Electro-Mechanical are exactly what the name BI-METAL implies: twoTHERMOSTATS different metals bonded together under heat and pressure to form a single strip of material. By employing the different expansion rates of the two materials, thermal energy can be converted into electro- Instrumentati on  Electro-Mechanical are exactly what the name BI-METAL implies: twoTHERMOSTATS different metals bonded together under heat and pressure to form a single strip of material. By employing the different expansion rates of the two materials, thermal energy can be converted into electro- Instrumentati on Instrumentati on Instrumentati on  Electro-Mechanical BULB AND CAPILLARY THERMOSTATS make use of the capillary action of expanding or contracting fluid to make or break a set of electrical contacts. Instrumentati on  Electro-Mechanical BULB AND CAPILLARY THERMOSTATS make use of the capillary action of expanding or contracting fluid to make or break a set of electrical contacts. Instrumentati on Instrumentati on  Electronic SILICON SENSORS make use of the bulk electrical resistance properties of semiconductor materials, rather than the junction of two differently doped areas. Instrumentati on  Electronic SILICON SENSORS make use of the bulk electrical resistance properties of semiconductor materials, rather than the junction of two differently doped areas. Instrumentati on Instrumentati on  Electronic INFRARED (IR) PYROMETRY measure the infrared energy emitted from an object in the 4–20 micron wavelength and convert the reading to a voltage Instrumentati on  Electronic INFRARED (IR) PYROMETRY measure the infrared energy emitted from an object in the 4–20 micron wavelength and convert the reading to a voltage Instrumentati on Instrumentati on Instrumentati on Instrumentati on  Electronic THERMOCOUPLES are formed when two electrical conductors of dissimilar metals or alloys are joined at one end of a circuit. Typically, they are built around bare conductors and insulated by ceramic powder or Instrumentati formed ceramic. on  Electronic THERMOCOUPLES are formed when two electrical conductors of dissimilar metals or alloys are joined at one end of a circuit. Typically, they are built around bare conductors and insulated by ceramic powder or Instrumentati formed ceramic. on Instrumentati on  (or thermallyResistive Devices sensitive resistors) are devices thatTHERMISTORS change their electrical resistance in relation to their temperature. They typically consist of a combination of two or three metal oxides that are sintered in a ceramic base material and have lead wires soldered to a semiconductor wafer or chip, which are covered with epoxy or Instrumentati on  (or thermallyResistive Devices sensitive resistors) are devices thatTHERMISTORS change their electrical resistance in relation to their temperature. They typically consist of a combination of two or three metal oxides that are sintered in a ceramic base material and have lead wires soldered to a semiconductor wafer or chip, which are covered with epoxy or Instrumentati on  Resistive Devices THERMISTORS Thermistors Positive Negative Temperature Temperature Coefficient (PTC) Coefficient (NTC) Instrumentati on  Resistive Devices THERMISTORS Positive Temperature Coefficient (PTC) TEMPERAT URE Instrumentati on  Resistive Devices THERMISTORS Positive Temperature Coefficient (PTC) TEMPERAT RESISTANC URE E Instrumentati on  Resistive Devices THERMISTORS Negative Temperature Coefficient (NTC) TEMPERAT URE Instrumentati on  Resistive Devices THERMISTORS Negative Temperature Coefficient (NTC) TEMPERAT RESISTANC URE E Instrumentati on Instrumentati on Instrumentati on  The metal Electronic sensing element is an RESISTIVE TEMPERATURE electrical resistor DEVICES that changes resistance with temperature. The element usually contains a coil of wire or conductive film with conductors etched or cut into it. It is usually housed in ceramic and sealed with ceramic cement or Instrumentati on  The metal Electronic sensing element is an RESISTIVE TEMPERATURE electrical resistor DEVICES that changes resistance with temperature. The element usually contains a coil of wire or conductive film with conductors etched or cut into it. It is usually housed in ceramic and sealed with ceramic cement or Instrumentati on Instrumentati on Instrumentati on Instrumentati on  SELECTING AND SPECIFYING TEMPERATURE SENSORS Instrumentati on  THERMISTORS provide high resolution, have the widest range of applications, are the most sensitive, and are low cost, but are nonlinear and have limited temperature range. SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  THERMISTORS provide high resolution, have the widest range of applications, are the most sensitive, and are low cost, but are nonlinear and have limited temperature range. SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  THERMISTORS provide high resolution, have the widest range of applications, are the most sensitive, and are low cost, but are nonlinear and have limited temperature range. SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  THERMOCOUPLES have the highest temperature region and are durable for high- vibration and high-shock applications, but require special extension wire. SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  THERMOCOUPLES have the highest temperature region and are durable for high- vibration and high-shock applications, but require special extension wire. SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  THERMOCOUPLES have the highest temperature region and are durable for high- vibration and high-shock applications, but require special extension wire. SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  RESISTIVE TEMPERATURE DEVICES are nearly linear and are highly accurate and stable, but they are large and expensive. SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  RESISTIVE TEMPERATURE DEVICES are nearly linear and are highly accurate and stable, but they are large and expensive. SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  RESISTIVE TEMPERATURE DEVICES are nearly linear and are highly accurate and stable, but they are large and expensive. SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  SILICON TYPES are low cost and nearly linear, but have a limited temperature range. SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  SILICON TYPES are low cost and nearly linear, but have a limited temperature range. SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  SILICON TYPES are low cost and nearly linear, but have a limited temperature range. SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  Accuracy is the sensor’s ability to measure the temperature’s true value over a temperature range. SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  Does the application require contact or non-contact sensing? SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  What temperature range is the sensor required to control or monitor? SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  What temperature range is the sensor required to control or monitor? Cryogenic Temperature Cases SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  What temperature range is the sensor required to control or monitor? Non Contact Extreme Temperatures below –18°C or above 538°C SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  What is the rate of temperature change of the application? SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  How tightly do you need to control or monitor the temperature? SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  How important is total system cost in the selection of the sensor? SELECTING AND SPECIFYING Instrumentati on TEMPERATURE SENSORS  ADVANTAGES AND DISADVANTAGES Instrumentati on  Electro-Mechanical BI-METAL THERMOSTATS Instrumentati on Instrumentati on  Electro-Mechanical Direct BI-METAL THERMOSTATS interface with application for fast response No additional circuitry/components required Available in both hermetic and non- hermetically sealed designs High current carrying capacity Wide operating temperature range Application/market-based pricing NASA qualified high reliability and military versions Instrumentati available Advantages on  Electro-Mechanical BI-METAL THERMOSTATS Less accurate than most electronic-based systems Larger size than electronic-based systems Creepage-type device cannot interface with electronic components Can fail “closed” at end of life Instrumentati Disadvantages on  Electro-Mechanical BULB AND CAPILLARY THERMOSTATS Instrumentati on Instrumentati on  Electro-Mechanical BULB AND CAPILLARY THERMOSTATS Control can be located at a significant distance from application being sensed Built-in overtemperature systems available Broad operating temperature range High current carrying capability Instrumentati Advantages on  Electro-Mechanical BI-METAL THERMOSTATS Large size Relatively expensive Limited number of potential applications Instrumentati Disadvantages on  Electronic Sensors SILICON SENSORS Instrumentati on Instrumentati on  Electronic Sensors SILICON SENSORS Less expensive than RTDs More linear than thermistors Easier to use than RTDs or thermocouples due to higher output IC types feature on-chip signal conditioning Many IC types include communication protocols with bus-type data acquisition systems Instrumentati Advantages on  Not as linearElectronic as RTDs Sensors SILICON Less accurate SENSORS than other electronic-based systems More expensive than thermistors or thermocouples Limited temperature range Slower thermal response than other electronic-based systems Typically larger than RTDs and thermistors Require larger package sizes for immersion Additional components/circuitry Instrumentati Disadvantages required to on  INFRARED (IR) Electronic Sensors PYROMETRY Instrumentati on Instrumentati on  Electronic Sensors INFRARED (IR) PYROMETRY Allows for non-contact measurement of moving objects or hazardous materials Can be used in conjunction with fiber optics for remote sensing Typical temperature range –18 to +538°C (0 to 1000°F) Accuracy to ±1% Instrumentati Advantages on  Electronic Sensors INFRARED (IR) PYROMETRY Accuracy can be affected by surface finish Field of view must be matched to target size Ambient temperature can affect readings Wavelength filter must be matched to the applicatioN Higher cost ($200+) can be even higher if control circuitry is Required Calibration can be difficult and costly Additional components/circuitry required to control application loads Dust, gas, or other vapors in the environment can effect the accuracyDisadvantages Instrumentati of the system on  Electronic Sensors THERMOCOUPLES Instrumentati on Instrumentati on  Electronic Sensors THERMOCOUPLES Small size provides rapid temperature response Relatively inexpensive Wide temperature range More durable than RTDs for use in high- vibration and high-shock applications ANSI established calibration types Instrumentati Advantages on  Electronic Sensors THERMOCOUPLES Must be protected from corrosive environments Smaller gage wire sizes are less stable and have a shorter operating life Use of plated-copper instrumentation wire results in errors when ambient temperatures change Special extension wires are required Reference junction compensation is required Less stable than RTDs in moderate or high temperatures Should be tested to verify performance under controlled conditions for critical applications Additional components/circuitry required to control application loads Instrumentati Disadvantages on  Resistive Sensors THERMISTORS Instrumentati on Instrumentati on  Resistive Sensors THERMISTORS Low component cost Fast thermal response Large change in resistance vs. temperature for more resolution Extremely small size means faster reaction to change in temperature and ability to use in variety of assemblies Linearized resistance types available High resistance values so no lead wire compensation Instrumentati Advantages necessary on  Resistive Sensors THERMISTORS Limited temperature range Lower temperature exposures than RTDs or thermocouples No established resistance standards Self heating can affect accuracy Non-linear resistance change requires additional components for accurate interpretation Increased component count decreases system reliability Additional components/circuitry required to control Instrumentati Disadvantages application loads on  Resistive Sensors RESISTANCE TEMPERATURE DETECTOR Instrumentati on Instrumentati on  Resistive Sensors RESISTANCE TEMPERATURE Very accurate and repeatable Wide temperature DETECTOR range –200 to +650°C (–328 to +1202°F) depending on type Extremely stable over time: >0.1°C/year drift Larger voltage output than thermocouples Excellent resistance linearity Resistance can be determined in the laboratory and will not vary significantly over time Area or point sensing Low variation for better interchangeability Can use standard instrumentation cable to connect to control equipment Established industry Advantages Instrumentati accepted resistance curves on  Resistive Sensors RESISTANCE TEMPERATURE DETECTOR Higher cost than thermistors or thermocouples Self heating of the RTD can affect overall system accuracy Larger size than thermistors or thermocouples Not as durable as thermocouples in high-vibration and high-shock environments Instrumentati Disadvantages on Instrumentati on ECE Elective 3 (2425_Term 1) BETELXT-NS-T-3A-T THANK YOU!