E3-TEMPERATURE MEASUREMENT METHOD.DOC - DNT 233...

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DNT 233Thermo-FluidLaboratory ModuleEXPERIMENT 3TEMPERATURE MEASUREMENT METHOD1.0OBJECTIVES1.1 To learn fundamental temperature measuring techniques usingi.Mercury-glass thermometerii.Thermocouple(type K)iii. Thermistoriv.Resistance Temperature Detector (RTD)v.Bi-metal thermometervi.Wet and dry bulb Temperature (Hygrometer)2.1To compare the accuracy of the various temperature measurement devices.2.0INTRODUCTION AND THEORYTemperature, measure of the relative warmness or coolness of an object.Temperature is measured by means of a thermometer or other instrument having a scalecalibrated in units called degrees. The size of a degree depends on the particulartemperature scale being used. A temperature scale is determined by choosing tworeference temperatures and dividing the temperature difference between these two pointsinto a certain number of degrees. The two reference temperatures used for most commonscales are the melting point of ice and the boiling point of water. On the Celsiustemperature scale, or centigrade scale, the melting point is taken as 0°C and the boilingpoint as 100°C, and the difference between them is divided into 100 degrees. On theFahrenheit temperature scale, the melting point is taken as 32°F and the boiling point as212°F, with the difference between them equal to 180 degrees.The temperature of a substance does not measure its heat content but rather theaverage kinetic energy of its molecules resulting from their motions. A one-pound block ofiron and a two-pound block of iron at the same temperature do not have the same heatcontent. Because they are at the same temperature the average kinetic energy of themolecules is the same; however, the two-pound block has more molecules than the one-pound block and thus has greater heat energy.The scale we use to measure temperature is "degrees" (°). There are threetemperature scales that are used today.i.The Kelvin (K) scale is used by scientists and for astronomical temperatures.ii.The Celsius scale (°C) is used in most of the world to measure air temperatures.iii.The Fahrenheit scale(°F) is used to measure temperatures at or near the surface.All three temperature scales are related to each other through the "triple point ofwater". The triple point of water is the temperature at which water vapor, liquid water, andice can coexist simultaneously. The triple point occurs at 0.01 °C (273.16 K or 32.02 °F).To convert from one temperature scale to another, we need to use the equations as below:1
DNT 233Thermo-FluidLaboratory Module1)Convert Celsius to Kelvin: K = °C + 2732)Convert Celsius to Fahrenheit: °F = 1.8(°C) +322.1Mercury in Glass ThermometerThe mercury in glass thermometer (figure 1) is a thermometer consisting ofmercury in a glass tube. Calibrated marks on the tube allow the temperature to beread by the height of the mercury column in the capillary tube which variesaccording to the temperature. Glass thermometerisaccurate,economicalinstrument that measurestemperature of liquids or gases. All of the glass

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Term
Fall
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RTD, Temperature measurement method

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