THERMOCOUPLE Seebeck effect- when two conductors of dissimilar metels are joined together to form a loop(thermocouple) and two unequal temp are imposed at the two interface connections,an electric current flows through the loop Peltier effect : a potential difference always exists between two dissimilar metal in contact with each other Thomson effect : A potential gradient exists even in a single conductor having a temp gradient

THERMOCOUPLE MATERIALS

DESIRABLE CHARACTERISTICS OF THERMOCOUPLE MATERIAL The emf produced per degree of temp change must be sufficient to facilitate detection and measurement Temp- emf relation should be linear It should maintain calibration without drift for longer period of time It should be highly resistant to oxidation, corrosion and contamination It should withstand high and fluctuating temp

RESISTANCE THERMOMETER (PLATINUM HAVING POSITIVE THERMAL COEFFICIENT)

THERMISTORS (Oxides of copper,nickel,iron,cobalt,uranium etc having negative thermal coefficient)

PYROMETER Pyrometry is a technique for measuring temp without physical contact It depends upon relationship between the temp of a hot body and electromagnetic radiation emitted by the body When a body is heated, it emits thermal energy known as ‘radiation’ Pyrometry is the technique for determining body’s temp by measuring its electromagnetic radiation Types - Radiation and Optical pyrometers

RADIATION PYROMETER

DISAPPEARING FILAMENT OPTICAL PYROMETER