Electrothermic Instruments

Electrothermic Instruments Points : Electrothermic Instruments, Definition, Thermal Instruments The thermal or electrothermic instruments are those instruments whose action depends upon the heating effect of the current under measurement. These instruments are used for measurement of current at high frequencies without any significant errors. In fact their chief field of application is in the measurement of current of frequencies above the range of moving-iron and electrodynamometer type instruments. At moderate frequencies they can be used for precision measurement of voltage. The thermal instruments are of following types:-
(i) Hot-Wire and Bi-metallic instruments
(ii) Thermocouple instruments
(iii) Bolometers