Using laser technology for level measurement in process control

May 2002 Level Measurement & Control

Laser instruments used for level control in process measurement use a semiconductor laser, which has the ability to flash on and off very rapidly. It measures distance by timing how long it takes a pulse of laser light to travel from the laser instrument to the object directly ahead and back again.

One of the main characteristics that gives laser its unique level measuring ability is based on the fact that it has a very short wavelength (compared to ultrasound and microwave radiation). This means that the beam of light emitted can be focused so that there is virtually no beam divergence. The laser can then be focused on an object without any interference from surrounding objects.

Another characteristic that plays a major role in lasers measuring ability stems from the fact that the laser radiation propagates through the medium at the speed of light. This means that very high update rates are achievable, with none of the 'lock-in' problems that can be experienced when using ultrasonic instruments. With laser instruments, the measurement is not at all dependent on the pressure or temperature of the medium, as the speed of light remains relatively unchanged through any gaseous medium. In applications, such as petrol or gas tanks where the density of the gaseous medium is unknown (and continually changing) laser instruments will give an accurate measurement without any calibration problems.

"Compared to other methods of level measurement laser is technologically much more advanced. It is faster, more accurate and easier to use than ultrasonic, radar, nuclear or mechanical methods. It appears that it will become the favoured method of level sensing as soon as it becomes price competitive with other existing technologies," concludes LaserM.

LaserM

011 314 4130

marketing@laserm.co.za

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