Measuring system for web movement speed - has no relative movement between web plane and transmitter and receiver

摘要

On one side of the plane there is a transmitter which sends towards the web of material a narrow ultrasonic beam in the plane at an angle different from 90 deg.. This ultrasonic beam is reflected from the web after striking it at the preset angle. A receiver on one side of the plane has the same angular adjustment to the plane as the transmitter. It receives an ultrasonic signal reflected from the web of material and detects in the signal a Doppler frequency shift proportional to the speed of movement of the web.