# Optical flowmeter

**URL:** <https://forumautomation.com/t/optical-flowmeter/3014>\
**Category:** Flow Measurement\
**Created:** [January 20, 2018, 8:07pm UTC](https://forumautomation.com/t/optical-flowmeter/3014 "2018-01-20T20:07:00Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![sivaranjith](https://forumautomation.com/letter_avatar_proxy/v4/letter/s/ba9def/32.png) [@sivaranjith](https://forumautomation.com/u/sivaranjith)\
**Post date:** [January 20, 2018, 8:07pm UTC](https://forumautomation.com/t/optical-flowmeter/3014/1 "2018-01-20T20:07:01Z")

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> ##Principle:

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:

 ![optical flowmeter](https://cdn.forumautomation.com/original/2X/5/5102d809a9e8705cb69acff4d4512c9209f81bab.png)

- 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:

## V=d/t

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