Interface level measurement is common in oil and gas, chemical industries. An interface is a limit between two immiscible liquids, due to its density difference.
The interface measurement finds the limit between the two liquids, therefore, to calculate the measurement of both quantities of liquid. You can use to pour only fluid from a tank that has two liquids.
Interface level measuring methods:
There are two technologies suitable, guided and magnetostrictive
Guided wave radar:
For single liquid level measurement, the guided wave radar reflects a signal from the air-liquid interface. The amount of reflected signal is the measure of level in the tank.
For interface level measurement there are two interfaces, air-liquid and liquid-liquid. The range of the second signal gives the interface level of the liquid tank.
In the case of a two-liquid interface with gas or vapour above, the relative permittivities of both gas and upper liquids must be accurately known to accurately measure the liquid-liquid interface
Another important factor in maximizing reflected power is the degree to which the microwaves disperse.
One way to compensate for the gas phase effect is to equip the instrument with a reference probe of fixed length oriented in such a way that its entire length is always above the liquid level.
Magnetostrictive level measurement:
The magnetostrictive meter is also an echo-based level instrument.
A magnetic float is placed in the metering rod of the magnetostrictive. The float produces torsional wave pulse on contact with the electromagnetic wave. The sensor on the top of the tank senses the torsional wave.
For interface level measurement, measuring rod has two floats having different densities. Such that each float can float above two liquid level. one to sense a liquid-liquid interface, and the other to sense the liquid-vapour interface.
The first torsional signal represents the total length and the second signal represents the interface level.