Question

Research ways to measure temperature. Find at least five different ways to measure temperature, each based on a different physical process or parameter. Explain why you might choose this method to measure temperature, what are the strengths and constraint of each method? (Keep your customer in mind!)

DO NOT cut and paste descriptions of the thermometers from the web. Explain the measurement in your own words.

Develop at least 15 questions you would like to ask the customer to help clarify his needs and guide your design.

Answer 1

1) Resistance Thermometer: The resistance of a conductor changes when it's temperature change, this property is used to measure temperature. In this thermometer uses change in electrical resistance of conductor to measure temperature. Discover by Sir Humphry, platinum is specially suited for this purpose. Resistivity of metal must be high otherwise large quantity of metal need to be used. Gold and silver are rarely used due to their low resistivity.

2) Thermistor: It is compact term of thermal+ resistor, generally composed of semiconductor material. Most thermistor have negative coefficient of temperature resistance I.e. their resistance decreases as temperature increases. This method is advantageous over other as it detects very small changes in temperature. Widely used in application which involves measurement in the range of -60 degree to 15 degree. The resistance of thermistor is ranges from 0 5 ohm to 0.75 M ohm. Highly sensitive device, exhibit highly non linear characteristics. Thermistor has very high negative temperature coefficient of resistance, which makes it an ideal transducer.

3) Thermocouple: When two metals having different properties are placed together, a voltage is generated at the junction, which is nearly proportional to temperature. This junction is called thermocouple. Thermo electric EMF depends upon the difference in temperature between hot junction and reference junction, usually reference junction is at 0 degree. It is used to measure temperature of about 1400 degree Celsius. It follows quadratic relationship. It is active transducer.

4) Pyrometer : Pyrometer is used to measure surface temperature by property of spectrum of thermal radiation, sometimes called radiometry, specially suited for measurement of moving objects. It is a gun like device very handy to use.

5) Thermometer: It is used to measure temperature using a mercury fitted inside glass tube, mercury is used because as it comes into contact of temperature, it turns from solid to liquid, and start expanding till highest temperature. Easy to used form normal temperature, mostly used for measuring body temperature. Nowadays Electronic or digital thermometer is used for accurate measurement of temperature.

Question:

1) what is measuring ranges of temperature.

2) which types of devices i.e. active or passive is required?

3) For what application it will be used?

4) Budget of customer ??

5) where it will be used???

6) which types of material is required i.e. semiconductor or conductor?

7) which type of device is required negative temperature coefficient or positive temperature coefficient?

8) what is minimum and maximum range of measurement?

9) what kind of temperature measurement is required??

10) Digital measurement device or analogue device??

11) For what application device is required, for medical or industrial purposes??

12) Accuracy expected??

13) which material is required for thermocouple??

14) what type of Device is needed?? Is it self generating or power required??

15) Computer accessibility??