Page 311 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

Fig 1 - 3

Frequency meter

Objectives: At the end of this lesson you shall be able to:
• state the types of frequency meters
• describe the principle, construction and working of a mechanical resonance (vibrating reed) type frequency
meter.

The following types of frequency meters are used for measuring power frequencies.
• Mechanical resonance type
• Electrical resonance type
• Electro-dynamic type
• Electro-dynamometer type
• Weston type
• Ratiometer type
• Saturable core type

The explanation given here is for mechanical resonance type frequency meter only as indicated below.
The trainees are advised to refer to books on electrical measuring instruments for learning about the other types
of frequency meters.

Mechanical resonance type frequency meter (vibration reed type)
Principle: The vibration reed type frequency meter shown in Fig 1 works on the principle of natural frequency.
Every object in the world has its natural frequency, depending upon its weight and dimensions. When an object
is kept in a vibrating medium, it starts vibrating, if the frequency of the medium attains the natural frequency of
the object.

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CITS : Power - Electrician & Wireman - Lesson 50-53