概述各类测速发电机式转速表,包括直流测速发电机、中频(400c/s)供电的交流测速机组、同步电机式交流测速机组,用于钻机转速测量都有一个共同的缺点,即不能反转。过去使用此类测速仪表必需加装换向开关,在钻机动力头反转之前切换或断开电路。但全液压钻机扭卸管时,反转频繁,很难做到经常切换开关,常致使仪表损坏。 Summarize all kinds of tachometer generator tachometer, including DC tachometer, AC (400c / s) power supply AC tachometer, synchronous motor type AC tachometer, used in drilling speed measurement has a common shortcomings, that is not anti turn. In the past, such a speedometer must be equipped with a reversing switch to switch or disconnect the circuit before the power head of the rig reverses. However, the entire hydraulic drill twist pipe, the reverse frequently, it is difficult to do often switch, often resulting in instrument damage.