In The Name of Allah The Most Beneficent The Most Merciful

1. In The Name of Allah The Most Beneficent The Most Merciful

2. ECE 4550:Biomedical Instrumentation Lecture:Temperature Measurement Engr. Ijlal Haider University of Lahore, Lahore

3. Temperature Measurement • The human body temperature is a good indicator of the health and physiological performance of different parts of the human body. • Temperature indicates: • Shock by measuring the big-toe temperature • Infection by measuring skin temperature • Arthritis by measuring temperature at the joint • Body temperature during surgery • Infant body temperature inside incubators • Temperature sensors type • Thermocouples • Thermistors • Radiation and fiber-optic detectors • p-n junction semiconductor (2 mV/oC)

4. ROUTES TO MEASURE TEMPERATURE Oral: By mouth Rectally: By rectum Axillary: Under the arm in the armpit Tympanic: In the ear

5. Importance of Temperature • 1st vital sign to any illness, system dysfunctionalities or fatalities • Fever associated to infection, severe trauma, allergies to medications & critical diseases • Hypothermia & Hyperthermia • Prevention of death & allow timely therapy for complications

6. Body Measurement Site

7. Source: http://nl.wikipedia.org/wiki/Hypothalamus Body Measurement Site • Best measurement site : Hypothalamus • Reflects the central or “Core” body heat • Base of the brain • Adjusting the temperature • Access is very inconvenient

8. Source: http://catalog.nucleusinc.com/generateexhibit.php?ID=2639&ExhibitKeywordsRaw=&TL=4294967295&A=2 Source: http://health.allrefer.com/pictures-images/esophagus.html Source: http://hon.nucleusinc.com/generateexhibit.php?ID=4537&ExhibitKeywordsRaw=&TL=4294967295&A=1027 Body Measurement Site • Pulmonary artery (PA), Esophagus and Bladder • Involve invasive thermometry • Very impractical for routine use

9. Source:http://www.patienthealthinternational.com/ncmprintchapter.aspx?type=article&param=500830Source:http://www.patienthealthinternational.com/ncmprintchapter.aspx?type=article&param=500830 Source: http://www.amazon.com/exec/obidos/tg/detail/-/B0002AHVZU/103-6985049-8479059?v=glance Body Measurement Site • Rectal • Incapable of responding quickly • Higher measured temperature

10. Source: http://www.emedicine.com/ent/images/1117ExtEar.jpg Source: http://www.actamed.co.uk/ProductDetails.asp?CategoryID=2&ProductCategoryID=43&ProductID=206 Body Measurement Site • The tympanic membrane (TM) i.e. Ear • Very near proximity to the hypothalamus • Reliable indicator • Infrared aural sensors are easily available

11. Advantages of IR Ear Thermometer Rapid response rate (<5s) Disposable plastic tips Little or no contaminations Pretty accurate & reliable Safe Easy to use Thermopile sensors

12. TYPES OF THERMOMETERS Digital Electronic: To be used for oral, rectal, and axillary Thermoscan - Digital: To be used for tympanic Mercury or glass: To be used for oral, rectal, and axillary

13. NORMS Orally: 97.6 - 99.6 degrees Fahrenheit Rectally: 99.6 - 100.6 degrees Fahrenheit Tympanic - manufacturers say to measure as for rectal Axillary: 96.6 - 98.6 degrees Fahrenheit

14. WHAT THERMOMETER SHOULD BE USED? Tympanic: Special device with plastic covers. Electronic: All routes. Probes that are red in color for rectal temperatures; blue in color for oral and axillary. Mercury: All routes. Red ends are rectal; blue ends oral and axillary.

15. DURATION FOR TAKING TEMPERATURES Tympanic: As long as it takes to push a button Electronic: Until the thermometer beeps Mercury Oral: Three minutes Mercury Rectal: Three minutes Mercury Axillary: Ten minutes

16. BE CAREFUL ON RECTAL AND AXILLARY TEMPS Always hold the thermometer in place while measuring both temperatures Always use lubricant with rectal temperatures Always remove clothing around axilla

17. READING THE THERMOMETER Mercury Fahrenheit thermometers are read by degree and 0.2 of a degree Long lines indicate degrees Short lines indicate 0.2 of a degree Four short lines between each long line (0.2, 0.4, 0.6, 0.8)

18. A T2  T1 T1 B B E = f(T1 –T2) Thermocouple Electromotive force (emf) exists across a junction of two dissimilar metals. Two independent effects cause this phenomena: 1- Contact of two unlike metals and the junction temperature (Peltier) 2- Temperature gradients along each single conductor (Lord Kelvin) E = f (T12 - T22) Advantages of Thermocouple fast response (=1ms), small size (12 μm diameter), ease of fabrication and long-term stability Disadvantages Small output voltage, low sensitivity, need for a reference temperature

19. A T2  T1 T1 B B E = f(T1 –T2) Thermocouple Empirical calibration data are usually curve-fitted with a power series expansion that yield the Seebeck voltage. T: Temperature in Celsius Reference junction is at 0 oC

20. Thermocouple Laws • 1- Homogeneous Circuit law: A circuit composed of a single homogeneous metal, one cannot maintain an electric current by the application of heat alone. See Fig. 2.12b • 2- Intermediate Metal Law: The net emf in a circuit consisting of an interconnection of a number of unlike metals, maintained at the same temperature, is zero. See Fig. 2.12c • Second law makes it possible for lead wire connections • 3- Successive or Intermediate Temperatures Law: See Fig. 2.12d • The third law makes it possible for calibration curves derived for a given reference-junction temperature to be used to determine the calibration curves for another reference temperature. T3 T1 T2

22. A T2 T1 B E = f(T1 –T2) Thermoelectric Sensitivity  For small changes in temperature: Differentiate above equation to find , the Seebeck coefficient, or thermoelectric sensitivity. Generally in the range of 6.5 - 80 V/oC at 20 oC.

23. Thermistors • Thermistors are semiconductors made of ceramic materials whose resistance decreases as temperature increases. • Advantages • Small in size (0.5 mm in diameter) • Large sensitivity to temperature changes (-3 to -5% /oC) • Blood velocity • Temperature differences in the same organ • Excellent long-term stability characteristics (R=0.2% /year) • Disadvantages • -Nonlinear • -Self heating • -Limited range

24. R3 R1 V vb va R2 Rt Circuit Connections of Thermistors Bridge Connection to measure voltage Amplifier Connection to measure currents

25. Radiation Thermometry The higher the temperature of a body the higher is the electromagnetic radiation (EM). Electromagnetic Radiation Transducers - Convert energy in the form of EM radiation into an electrical current or potential, or modify an electrical current or potential. Medical thermometry maps the surface temperature of a body with a sensitivity of a few tenths of a Kelvin. Application Breast cancer, determining location and extent of arthritic disturbances, measure the depth of tissue destruction from frostbite and burns, detecting various peripheral circulatory disorders (venous thrombosis, carotid artery occlusions)

26. http://en.wikipedia.org/wiki/Blackbody_radiation

27. Radiation Thermometry Sources of EM radiation: Acceleration of charges can arise from thermal energy. Charges movement cause the radiation of EM waves. The amount of energy in a photon is inversely related to the wavelength: Thermal sources approximate ideal blackbody radiators: Blackbody radiator: an object which absorbs all incident radiation, and emits the maximum possible thermal radiation (0.7 m to 1mm).

28. Fused silica 100 Sapphire Arsenic trisulfide Thallium bromide iodine 50 10 0 1 10 100 Wavelength, mm All thermal detectors 100 Indium antimonide (InSb) (photovoltaic) 60 Lead sulfide (PbS) 20 0 1 2 3 4 5 6 7 8 Wavelength, mm Thermal Detector Specifications • Infrared Instrument Lens Properties; • pass wavelength > 1 m • high sensitivity to the weak radiated signal • Short response • Respond to large bandwidth • Thermal Detectors • -Law sensitivity • Respond to all wavelength • Photon (Quantum) Detector • -higher sensitivity • -Respond to a limited wavelength Fig. a Fig. a) Spectral transmission for a number of optical materials. (b) Spectral sensitivity of photon and thermal detectors. Fig. b

29. Radiation Thermometer System Figure 2.15 Stationary chopped-beam radiation thermometer

30. Application of Radiation Thermometer Measuring the core body temperature of the human by measuring the magnitude of infrared radiation emitted from the tympanic membrane and surrounding ear canal. Response time is 0.1 second Accuracy of 0.1 oC

31. Fiber-Optic Temperature Sensors • Small and compatible with biological implantation. • Nonmetallic sensor so it is suitable for temperature measurements in a strong electromagnetic heating field. Gallium Arsenide (GaAs) semiconductor temperature probe.The amount of power absorbed increases with temperature

32. Advantages of IR Ear Thermometer Rapid response rate (<5s) Disposable plastic tips Little or no contaminations Pretty accurate & reliable Safe Easy to use Thermopile sensors

33. Shorter λ Source: http://en.wikipedia.org/wiki/Infrared_radiation visible IR microwave Higher f Humans, at normal body temperature, radiate most strongly in the infrared, at a wavelength of about 10 microns Source:http://imagers.gsfc.nasa.gov/ems/infrared.html Source: http://coolcosmos.ipac.caltech.edu//cosmic_classroom/ir_tutorial/what_is_ir.html IR Technologies • All Bodies emit E-wave & IR radiation • IR radiation: • Emitted from an object • Reflected off a surface

34. Wavelength emitted depends on Tempt. IR Technologies Hot objects emit more of their light at short wavelengths Cold objects emit more of their light at long wavelengths

35. IR Technologies • IR wavelength = 0.000075 - 0.1 cm • IR frequency = 300 GHz - 400 THz • Total energy radiated: P = σ A T4 P = energy radiated per second σ = 5.6703 x 10-8 watts/m2 K4 Stefan-Boltzmann constant,A = surface area of the radiating object T = temperature (Kelvin scale) Hot objects = Higher Power Cold objects = Lower Power

36. IR Technologies • IR tempt. measurement is very competent • Fast • Dynamic • Non-contact • Precise • High sensitivity • Higher security • Low power requirements • Low circuitry costs • Simple circuitry • high resolution • reasonable fields of view • Wide area of applications

37. THANK YOU Read for your knowlede