Describe The Construction And Working Of Thermoelectric Thermometers ?
A thermoelectric thermometer is used for the measurement of temperatures both low and high. Principle: Its working is based on see beck effect thermocouples of different metals are constructed depending upon the temperature to be measured. Construction: The wires forming the thermocouple are welded together at one end and this end forms the hot junction. The portions of the wires near the hot junction are properly insulated from each other by enclosing them in a hard-glass capillary tube C.T. the wires are passed through mice discs D, which are fitted one above the other in a porcelain tube T. the ends of these wires are connected to the terminals T1 and T2 to these terminals are connected compensating leads L1 and L2 of the same materials as those forming the thermocouple itself. By so doing the cold junction is shifted to a convenient place where a constant temperature of OC is maintained. By keeping hot junction at different known temperatures the corresponding values of thermo are noted using distal voltmeter in the circuit of thermocouple. The digital voltmeter gives its internal resistance is very high (about 10 Ω). A graph plotted between the temperature of hot junction and Themo the curve so obtained is called calibration curve. To find the unknown temperature of a given bath the hot junction is placed in the given bath. The thermo so generated is measured. The temperature corresponding to this value of thermo is determined from the calibrations curve. Note it is important to note that thermocouple should not be used to measure the temperature above the neutral temperature.
