Temperature comes under one of the key variable which is measured and calibrated while dealing with Instrumentation and control in all level of processes and industries . If you are looking for presentations related to temperature measurement , process flow and other measurements such as pressure and flow , you will get number of downloadable presentations that you can take as a reference for your assignments . In today’s presentation of temperature measuring instruments , we will discuss some of the keypoints and types of thermometers used for temperature measurement .Moreover we are highlighting the working principles of the instruments and how they are different from each other .
Temperature measurement devices PPT
Here is the downloadable temperature measuring instruments presentation with the download link .You can view it online as well as download it .
Here are some of the fundamental point that we are discussing in the above presentation .In this temperature measuring devices presentation , we are talking about four basic types of temperature measuring devices and what are the principle of operation for each .To ease it , we are giving examples for each of the devices alongwith differences and similarities among each temperature measuring device .
Temperature measuring devices discussed in PPT are
- Mechanical (it includes liquid-in-glass thermometers, bimetallic strips, etc.).
- Thermojunctive ( such as thermocouples).
- –Thermoresistive (it includes RTDs and thermistors).
- –Radiative (such as infrared and optical pyrometers).
For the first one , principle of operation is as follow : A change in temperature causes some kind of mechanical motion, typically due to the fact that most materials expand with a rise in temperature. Mechanical thermometers can be constructed which use liquids, solids, or even gases as the temperature-sensitive material. And the mechanical motion is read on a physical scale to infer the temperature.
The most common and well-known thermometer is the liquid-in-glass thermometer. In this case , working principle is : As the temperature rises, the liquid expands, moving up the tube. The scale is calibrated to read temperature directly.Usually, mercury or some kind of alcohol is used for the liquid .
Bimetallic strip Thermometer
Two dissimilar metals are bonded together into what is called a bimetallic strip .Suppose metal A has a smaller coefficient of thermal expansion than does metal B. As temperature increases, metal B expands more than does metal A, causing the bimetallic strip to curl upwards .
Radiative temperature measuring devices
It is also termed as radiative pyrometry. In this case , Radiative properties of an object change with temperature. So, radiative properties are measured to infer the temperature of the object.In this case there is no physical contact with the object whose temperature is being measured.There are number of advantages of using this method of measurement .Few of its advantages include : Very high temperatures can be measured.The fundamental equation for radiation from a body is the Stefan-Boltzmann equation, where
- E is the emissive power radiated per unit area (units of W/m2).
- is the emissivity, defined as the fraction of blackbody radiation emitted by an actual surface.
- The emissivity must lie between 0 and 1, and is dimensionless.
- Its value depends greatly on the type of surface. A blackbody has an emissivity of exactly 1.
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