DC Ammeter: The PMMC galvanometer constitutes the basic movement of a dc ammeter. Since the coil winding of a basic movement is small and light, it can carry only very small currents. When large currents are to be … (Read More)

Thermocouple Principle and Types of Thermocouple: Thermocouple Principle consists of a junction of two dissimilar wires, so chosen that a voltage is generated by heating the junction. The output of a thermocouple is delivered to a sensitive dc microammeter. (Calibration is made … (Read More)

Various Factors of Frequency Effect on Calibration: The Various Factors of Frequency Effect on Calibration such as: Skin effect Non uniform distribution of current along the heater wires Spurious capacitive currents 1. Skin Effect: The skin effect causes a higher reading at higher frequencies, especially if … (Read More)

Measurements of very Large Currents by Thermocouples: Thermocouples instruments with heaters large enough to carry very large currents may have an excessive skin effect. Ordinary shunts cannot be used because the shunting ratio … (Read More)