6. TEMPERATURE MEASURING
SCALES
• Centigrade
Denoted by °C
Water freezes at O°C and boils at 100°C
• Fahrenheit
Denoted by °F
Water freezes at 32°F and boils at 212°F
• Kelvin
Denoted by K
Water freezes at 273K and boils at 373K
12. BI METALLIC STRIP THERMOMETER
• Bimetallic strip thermometers
• Dial
• Convenient
• Inexpensive
• Poor accuracy and precision
13. THERMOCOUPLES
• Two different metals are joined together
• Change in temperature cause magnetic field
• Seekbeck effect
• Voltage can be interpreted in readable temperature
14. THERMOCOUPLES
• Seebeck Effect
• Any conductor subjected to a temperature gradient generates a potential difference
• Working principle of thermocouples
15. THERMOCOUPLES
• Type K
• the most common general purpose thermocouple
• −200 °C to +1350 °C
• constituent metals is Nickel
• Cause magnetic field @ curie temperature
• @ 354 °C.
16. THERMOCOUPLES
• Type E
• It is non-magnetic.
• Cryogenic use
• 68 µV/°C
• Type J
• Less popular then K type
• −40 to +750 °C
• 50 µV/°C
• The Curie point of the iron 770 °C
18. RTD
• Electronic technology
• resistance temperature detectors
• correlating the resistance
• element is usually quite fragile
• Pure material, typically platinum, nickel or copper
• slowly replacing the use of thermocouples (<600 C)
24. IC TEMPERATURE SENSORS
• Two terminal integrated circuit
• Produce an output current
• Sensor package is small
• low thermal mass and a fast response
• 55 to 150°C