What are non-invasive methods of level measurements? Where are they used?
In applications where the contact with the material is prohibitive either due to environmental conditions outside the vessel or inside the vessel the non-invasive methods are required. Basically energy is beamed at the target material and the reflected wave is detected. The time of flight is measured. If the velocity of the wave is known the distance can be calculated. Energy in different forms that may suit any particular application can be used. This gives rise to a number of types of level measuring instruments based on various forms of energies. There are instruments based on transmission of pulse burst of sonic and ultrasonic energy and the receipt of its echo. There are instruments based on electromagnetic energy using the microwave Radar principle. There are instruments using coherent light based on the Laser principle. There are instruments based on Nuclear energy. Each of the methods has their advantages and disadvantages. A judicious choice should be made after giving due con
