A magnetostrictive liquid level sensor is a type of device used to measure the level of liquid in a container or tank. It works based on the principle of magnetostriction, which refers to the property of certain materials to change their shape or dimensions when exposed to a magnetic field. The magnetostrictive liquid level sensor is commonly used in industrial and commercial applications due to its accuracy and reliability.
Here's how the magnetostrictive liquid level sensor operates in liquids:
Construction:
The sensor consists of a rigid tube made of a magnetostrictive material, typically an iron-nickel alloy, inserted vertically into the tank or container holding the liquid. A float, usually made of a non-magnetic material, is attached to the sensor's stem and floats on the liquid's surface. The float's position changes according to the liquid level in the tank.
Electrical Pulse Generation:
At the base of the sensor tube, there is an electrical conductor called the waveguide. A brief electrical pulse is sent down this waveguide, creating a magnetic field around it.
Interaction with Magnetic Field:
When the electrical pulse reaches the point where the magnetic float is positioned, it induces a magnetic field in the float itself. The magnetic field of the float interacts with the magnetic field of the waveguide, leading to the generation of torsional mechanical stress (magnetostriction) in the waveguide material.
Reflection of Torsional Pulse:
The torsional mechanical stress in the waveguide creates a mechanical wave, which travels in both directions along the length of the waveguide. When this wave reaches the bottom of the tube, some of it is reflected back towards the top of the tube.
Time-of-Flight Measurement:
The magnetostrictive liquid level sensor measures the time it takes for the mechanical wave to travel from the base of the tube to the top (reflect back). This time interval, known as the "time-of-flight," is precisely measured.
Level Calculation:
The magnetostrictive liquid level sensor knows the speed at which the mechanical wave propagates in the waveguide material. By multiplying the time-of-flight by the wave propagation speed, the sensor can accurately determine the distance from the base of the tube to the magnetic float's position. This distance corresponds to the level of the liquid in the tank.
Output and Calibration:
The sensor converts the level measurement into an appropriate output signal, such as a 4-20mA current loop or digital communication protocol. Calibration may be necessary to ensure accurate readings, which can involve setting the zero point (empty tank) and span (full tank) to match the tank's physical dimensions.
The advantage of using a magnetostrictive liquid level sensor is its ability to provide real-time and accurate level measurements, even in challenging conditions with high turbulence, foam, or vapor. It is widely used in various industries, including chemical processing, oil and gas, water treatment, and storage tank monitoring, among others.