Electrodynamic Frequency Meter – Working – Construction – Range – Advantages – Disadvantages


Electrodynamic Frequency Meter

Electrodynamic frequency meters/moving coil frequency meters are ratiometer types of instruments. These meters are used to measure the frequency of high voltage ranges and too low voltage ranges. These frequency meters provide accurate frequency readings. These frequency meters consist of two moving coils and a rectifier circuit.


This frequency meter consists of the two moving coils connected to each other at right angles on a shaft and a pointer is also connected with this shaft. These two moving coils are connected with their bridge rectifiers. This circuit consists of a capacitor which is connected in series with the bridge rectifier of the first moving coil C1 connected to the DC Supply. The direct current (rectified current) flows through a series of resistance to the bridge rectifier and to the second coil C2.


These meters depend on the value of resistance and a capacitor. These frequency meters have ranges of 40 to 60 Hz, 1200 to 2000 Hz, and 8000 to 12000 Hz.

Working of Electrodynamic Frequency Meter

When the frequency is connected to the supply, the rectified currents I1 and I2 pass through the moving coils C1 and C2. When these coils come to rest position, their torques become equal but in opposite directions.

These frequency meters have linear frequency scales.

The readings are independent of voltages.

These frequency meters can be used over a wide range of voltage and at too low a voltage range.


The rectifiers produce distortions which result in an inaccurate reading of frequency.

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