频率计

例句：

1. 1. The frequency meter is used to measure the frequency of light waves.
   频率计用于测量光波的频率。
2. 2.The engineer used the frequency meter to check the accuracy of the equipment.
   工程师使用频率计检查设备的准确度。
3. 3.The frequency meter was used to detect the presence of a specific frequency in the signal.
   频率计被用来检测信号中特定频率的存在。