Measurements of very Large Currents by Thermocouples: 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 will be affected by the relative inductance and resistance, resulting in a frequency effect. …
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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 the heater wire is small. A low current instrument …
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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 with dc or with a low frequency, such as 50 cycles, and applies …
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DC Ammeter: 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 measured, it is necessary to bypass a major part of the current through a …