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Prepared by: Tyler Whipple Dept. of Electrical and Computer Engineering Utah State University

ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors Resistance Thermometer Detector (RTD). Prepared by: Tyler Whipple Dept. of Electrical and Computer Engineering Utah State University (435)797-3054 (ECE Dept.). 3/20/2012. Outline. Reference list To further explore

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Prepared by: Tyler Whipple Dept. of Electrical and Computer Engineering Utah State University

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  1. ECE5320 MechatronicsAssignment#01: Literature Survey on SensorsResistance Thermometer Detector (RTD) Prepared by: Tyler Whipple Dept. of Electrical and Computer Engineering Utah State University (435)797-3054 (ECE Dept.) 3/20/2012

  2. Outline • Reference list • To further explore • Major applications • Basic working principle illustrated • A typical sample configuration in application (application notes) • Major specifications • Limitations • And many more relevant issues in applications (such as, how to choose, cost information, where to buy etc.) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  3. Reference List • Basics and selection of RTDs http://www.omega.com/rtd.html • General overview of Resistance thermometer http://en.wikipedia.org/wiki/Resistance_thermometer • RTD equations and circuit layout http://www.dataforth.com/catalog/pdf/an105.pdf • Applications, Pro/con RTDs http://www.azom.com/article.aspx?ArticleID=2339 • Complete guide to RTDs http://www.branom.com/literature/rtd.html • RTD vs thermocouple http://ultra-nspi.com/information-central/rtd-termocouple-comparison/ ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  4. To Further Explore • Calibration and standards information information hhttp://www.nist.gov/meas-services/ • Detailed information on RTD types http://www.omega.com/toc_asp/frameset.html?book=Temperature&file =RTD_Gen_Specs_Ref ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  5. Major Applications • Measure temperature for industrial applications • Textile production • Petrochemical processing • Food processing • Etc. • Used in applications measuring temperatures <600°C • Input for temperature controllers, transmitters, and digital readouts ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  6. Basic Working Principal • Determine temperature by measuring resistance in a wound wire element with temperature sensitive resistance and correlating it to temperature • Since resistance ideally varies linearity with temperature, changes in resistivity can be converted to changes in temperature which can be read by a temperature controller or mulitmeter ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  7. General RTD Circuit The schematic shows a basic 2-wire resistive temperature detector Figure from: http://en.wikipedia.org/wiki/File:Twowire.gif ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  8. Types of RTD Elements • Carbon resistor element • Inexpensive and reliable at low temperatures • Strain free element • Used up to 961.78 °C • Susceptible to shock and vibration damage • Thin film element • Less stable, limited temperature rage • Used < 300°C ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  9. Types of RTD Elements • Wire-wound element • Higher accuracy for wide temperature ranges • Coiled elements • Element can expand freely over temperature • High durability ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  10. RTD Types Thin Film RTD Coiled Element RTD http://en.wikipedia.org/wiki/Resistance_thermometer ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  11. RTD Element’s Material • Usually RTD elements are made of platinum, copper or nickel • Platinum • Highly linear resistance to temperature relationship over large temperature range • Usually best choice • Copper • Although very linear relationship, copper oxidizes at moderate temperature • Nickel • Limited temperature range due to non linear relationship ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  12. Advantages of RTDs • High accuracy • Low drift • Constant measurements • Wide operating range • Suitable for precision applications • 3-4 wire RTDs offer higher precision • Immune to electrical noise ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  13. Advantages of RTDs • Absolute measurements • Do not require reference point • High Output • Allows for simpler indication and control equipment • No amplifiers required which saves money and increases reliability ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  14. Limitations • Temperature range usually <660°C • Above 660°C platinum becomes increasingly susceptible contamination by impurities from metal sheath of thermometer • Less sensitive to small changes in temperature and slower response time than thermistors • No point sensing • Affected by shock and vibration • Requires multi-wire operation ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  15. Major Specifications • Metal Type • Temperature Range • Immersion/Surface measurement • Ruggedness • Accuracy ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  16. Accuracies for RTDs This table outlines generalized accuracies for RTDs throughout potential temperature ranges ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  17. Selection Process for RTDs • Geometry of measurement • Surface or immersion • Area or point sensing • The outer diameter of the tube. • The temperature range to be measured • The required length of immersion • How the RTD is to be inserted, and how best it can be supported or mounted. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  18. Cost Information • Resistive thermometer detector • Thin film platinum $1-$2.6 each package of 100 • Ultra precise immersion RTD $55-$101 • General Purpose RTD Probe with Metal Strain Relief $66-$72 • RTD Elements with 36 Inch Lead Wire form 2, 3 or 4 Wire RTD Sensor Probe $45 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  19. Where to Buy • Omega • Selection of many types of RTDs of varying amperage ratings and application • Has thermowells, temperature controllers, and accessories • Suggests additional components for selected RTDs and applications • Newark • Discount on bulk purchases • Large selection ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  20. Alternative: Thermocouple Comparing RTD to Thermocouple RTD Thermocouple Inexpensive Simple, Rugged High Temperature Tip Temperature Sensing Least Sensitive Non-Linear Low Stability • Good Stability • High Accuracy • Area Temperature sensing • Current source required • Slow Response time • Higher Cost ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

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