ABSTRACT
Temperature scales aim at using a common basis for temperature measurements. Thermocouples are widely used for temperature measurements in fluid streams. All temperature scales are based on some easily reproducible states, such as the freezing and boiling points of water, also called the ice point and the steam point. An extension of the thermometric scale is therefore made by introducing further fixed points, using substances other than water. The fixed points are laid down in what is known as the International Practical Temperature Scale. The change of pressure as a result of the change of temperature of the fluid is used for temperature measurement. The phenomenon of thermal expansion is made use of for temperature measurement in a number of temperature sensing devices. Thermometer is a general name given to thermometric measuring devices. Some of the commonly used thermometers are the mercury-in-glass thermometer, Beckmann thermometer, and gas thermometer.
