Optical flowmeter


Optical flowmeter uses light reflection to measure the velocity of the flow stream. It measures the time of flight of light to measure the flow of a stream.

##Construction and Working:

  • A dual beam laser is used as the source

  • Opposite sides of the pipeline is attached with optical window to let the light into the pipeline.

  • The light detecting sensors are placed at an inclination to the straight line path of the light.

  • The light detected is then converted into an electrical signal and then signal processed.

  • The light is let pass through the optical window and the light propagate through the fluid and comes out through the optical window at the other end.

  • If there is no fluid flow in the pipeline, the light goes straight and cannot be detected by the sensors.

  • If fluid flows through the pipeline. The incident light hits the particles in the fluids, the light gets scattered and deviates from the main path.

  • The deviated light is getting detected by the detector. Consider this happens at the first sensor. Then the particle moves further to the second beam of light.

  • The same happens for the second beam. The light beam gets deviated and detected at the second sensor. The time delay between the two successive pulse is measured.

  • This time delay is proportional to the flowrate of the stream, desicribed by the equation:


Where, v = Velocity of particle d = Distance separating laser beams t = Time difference between sensor pulses