Laser Doppler Anemometer

Laser Doppler anemometry ( LDV ), also known as laser Doppler anemometry ( LDA ) technology, is a doppler laser anemometer that is another type of anemometer used in industry. This Doppler optical technique is used to measure the velocity of turbulent currents for clear and translucent fluids and vibrations with matte and glossy flow surfaces. In industry and science, LDA (Laser Doppler Anemometer) or laser Doppler is used, which shows acceptable accuracy without moving parts and without the need for calibration and flow measurement in the opposite direction, and can be used for various chemicals, high temperatures. , Rotating machines, etc. are used.

The working principles of this anemometer are as follows:

A continuous laser wave

Optical transmission equipment such as wave splitters and focusing lenses

Optical equipment for receiver, comparator, concentrator and filter of interference wave and light detector

The corresponding conditioner and processor signal

Of course, in more advanced models, they can include a bus system and an angular encoder.

Usually a Bragg Cell laser beam is used. Bragg cell is a glass crystal with a vibrating crystal peso attached to it. Vibration causes the acoustic waves of the optical network to act.

The output of Bragg Cell is two beams with the same intensity and frequency f0 and f shift. By focusing the rays on the optical fiber, these waves reach the probe. In the probe, these parallel waves focus on the desired fluid with the help of a lens and intersect each other.