WL-147 WELLHISE HT522 CONTACTLESS TACHOMETER REVOLUTION METER is a device used to measure the revolution of a rotating object. It can be used as non-contact or contact, which means that the device does not need to contact an object to make a measurement. The HT522 model is often used to measure the rotational speed of industrial machines, determine engine speed, control propeller speed and similar applications. The device is especially important for monitoring the speed of rotating parts and evaluating their performance.