A magnetostrictive liquid level sensor is a type of level measurement device used to determine the liquid level in various industrial applications. While these sensors are designed to operate in liquids, they can be adapted to work in gases with the help of appropriate adjustments and considerations.
The basic principle of a magnetostrictive liquid level sensor involves utilizing the magnetostrictive effect. The magnetostrictive effect is a phenomenon in which certain materials change their shape or dimensions when exposed to a magnetic field. In this sensor, a magnetostrictive wire or rod made of ferromagnetic material (e.g., nickel-iron alloy) is used as the sensing element.
Here's how the magnetostrictive liquid level sensor operates in gases:
Sensor Construction: The sensor typically consists of a magnetostrictive wire or rod housed inside a protective tube or stem. The stem is made from non-magnetic and corrosion-resistant materials to ensure the sensor's durability in gas environments.
Installation: The sensor is installed vertically within the gas-containing vessel, and the length of the sensor is chosen to match the full height of the vessel or the desired measurement range.
Pulse Generation: To initiate the level measurement, an electrical pulse is sent along the magnetostrictive wire by an electronic control unit. This pulse creates a magnetic field around the wire.
Interaction with Liquid: When the magnetic field reaches the position of the liquid-gas interface, it interacts with the ferromagnetic liquid-gas boundary, causing a mechanical stress or strain in the magnetostrictive wire at that point.
Reflection of the Pulse: The mechanical stress created in the wire generates a torsional wave (also known as a "guided wave") that travels back up the length of the magnetostrictive wire.
Detection: A magnetic pickup or waveguide sensor is placed on the sensor tube to detect the arrival time of the torsional wave. The sensor detects the time it takes for the pulse to travel from the transmitter to the gas-liquid interface and back to the receiver.
Calculation: The electronic control unit measures the time-of-flight of the pulse, which is directly proportional to the distance from the transmitter to the liquid-gas interface. By knowing the total length of the sensor and the time taken, the level of the liquid in the gas can be accurately determined.
Output: The level information is then converted into an appropriate output signal, such as a 4-20mA current signal or a digital value, which can be displayed on an indicator or transmitted to a control system for further processing.
It is essential to note that using a magnetostrictive liquid level sensor in gases requires careful consideration of the gas's properties and the sensor's design to ensure accurate and reliable measurements. Additionally, the sensor should be calibrated and configured properly for gas applications to account for any environmental variations and challenges unique to gas level measurements.