Thermometers

• To make thermometers more sensitive increase volume of

  The bulb
• To increase sensitivity 


  Decrease diameter of the tube
• Thermocouple


  2 wires of metal joined
• Thermocouple


  If 2 wires are at different temps a electric field will be created whi ch enables electrons to travel
• The voltage of a thermocouple is dependent on

  Temp and metal chosen
• Advantages of using thermocouples

  Fast response time,robust, wide temp range
• Temp range of thermocouple

  -250 to 2000
• Digital thermometers can't measure

  High temps
• To convert from degrees kelvin to degrees Celsius you add

  273
• Disadvantage of thermocouple 


  Hard to callibrrate
• An application of thermistors

  Fire alarms
• Rotary thermometers

  The coiled bimetallic strip expands and touches a calibrated pointer when temp increases
• Rotary used in 


  Simple construction,allows general usage such as greenhouses and fridge
• Infra red 


  Extremely accurate when detects wavelengths of various radiation
• Usage of infrared 


  In hospitals to determine ones temp
• Cons of infra red

  Can only detect surface temp and affected by radio waves and ambient conditions
• Which temp measuring device is more accurate than a digital thermometers

  Temp probe