转速计

例句：

1. 1. The speedometer on the car shows the current speed.
   汽车上的转速表显示当前速度。
2. 2. The driver needs to check the tachometer before starting the engine.
   驾驶员在启动发动机前需要检查转速表。
3. 3. The engineer used a tachometer to measure the engine's RPM.
   工程师使用转速计测量发动机的转速。