Frequency meter

Japanese: 周波数計 - しゅうはすうけい（英語表記）frequency meter

A general term for measuring instruments that measure frequencies from radio waves to AC power. There are various operating principles depending on the frequency to be measured. For commercial frequencies, there are direct-reading instruments such as vibrating reed types and ratio meter types, as well as the Lissajous figure method, in which a figure is drawn on the observation screen of an oscilloscope and the frequency is calculated from the shape, and the stroboscope method. In the audible frequency range, there are AC bridge methods and CR charge-discharge type (discharge by a capacitor and resistor) frequency meters. For frequencies above a few megahertz, absorption frequency meters are used, as well as Lecher wire (two parallel lines) wavelength meters and frequency counters.

[Toshiharu Takao]

Vibration Reed Frequency Meter

It is used to measure AC frequencies below a few hundred hertz. When a large number of thin steel leaf springs (vibrating pieces) with slightly different natural frequencies are fixed in a row and placed in an AC magnetic field whose frequency is to be measured, only the vibrating pieces with a natural frequency equal to the frequency of the wave to be measured resonate and vibrate violently. This is used to measure frequency.

[Toshiharu Takao]

Ratio-type frequency meter

The AC voltage whose frequency is to be measured is applied to two electrical circuits with different frequency characteristics, and the ratio of the flowing currents is measured with a ratio meter to determine the frequency.

[Toshiharu Takao]

Stroboscope method

A strobe disk with a circumference divided into m equal parts and depicting light and dark areas is rotated N times per second by a synchronous motor, and illuminated with a neon tube that flashes with an alternating current of the frequency f Hertz to be measured.

When the condition is satisfied, the strobe disk pattern appears stationary. This phenomenon is used to measure frequency.

[Toshiharu Takao]

AC Bridge Method

The balance condition of an AC bridge is related to frequency. This is used to measure frequency, and a typical example is the Campbell bridge.

[Toshiharu Takao]

Absorption Frequency Meter

Also known as an absorption wavemeter, a resonant circuit is created using inductance and capacitance (electrostatic capacity), and a voltage of unknown frequency is applied to this, adjusting the capacitance to cause resonance and measure the frequency.

[Toshiharu Takao]

[Reference] | Stroboscope

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

電波から電力用交流までの周波数を測る計測器の総称。測ろうとする周波数によって種々の動作原理のものがある。商用周波数程度では振動片型、比率計型などの直読型の計器のほか、オシロスコープで観測画面上に図形を描かせ、その形から周波数を求めるリサジューの図形による方法、ストロボスコープ法などがある。また可聴周波数の範囲では、交流ブリッジによる方法、CR充放電型（コンデンサーと抵抗による放電）の周波数計などがある。さらに数メガヘルツ以上の高い周波数範囲になると、吸収型周波計が用いられ、さらにレッヘル線（平行二線路）波長計、周波数カウンターなども使われる。

［高尾利治］