The requirements for strict process controls, reduced waste, automated systems and reliable accuracy mean that level sensors are vital, both industrially and in the household. Depending on the application, there are a variety of liquid level sensors that meet the needs of different applications and environments.
What is a Liquid Level Sensor?
Designed to detect, measure and regulate levels of a particular free-flowing substance within a contained area, level sensors are predominantly a tool used to monitor liquid levels. They can also be used to monitor solids such as powders.
Simple liquid level sensors can be used to identify the point at which a liquid falls below a minimum or rises above a maximum level. Many, more advanced liquid level sensors can relay the specific volume of liquid in a container relative to the minimum/maximum levels, to provide a continuous measurement of volume.
Liquid level sensors have advanced significantly over many years. Today, a variety of technologies can be used for the process of level measurement. Liquid Level Sensor Applications Liquid level sensors have a vast range of applications, both industrially and within regular, everyday machines. Cars and other vehicles use liquid level sensors to monitor a variety of liquids, including fuel, oil and occasionally also specialist liquids such as power steering fluid. Level sensors can also be found in industrial storage tanks, slurries, and at water treatment plants. Water level sensors can even be found in household appliances such as coffee machines.
Many types of liquid level sensors are durable, which means they can withstand vibrations, extreme temperatures and hazardous materials.
Types of Liquid Level Sensors
There are several different types of liquid level sensors that can be used to detect the specific level of a liquid. One of the most commonly used types of liquid level sensors relies upon a magnetic float, which rises and falls as the liquid level in the container changes. Once the liquid, and therefore, the float and magnet, reaches a defined level, a reed magnetic switch is triggered. Commonly, there is a switch towards the top and the bottom of the container, allowing the detection of minimum and maximum levels of liquid. Many liquid level sensors also include a protective layer to shield the magnet from turbulence or interference from direct contact with the liquid.
Another common type of liquid level sensor is known as a conductive sensor, which can only be used to measure liquids which conduct electricity. A conductive sensor includes a source of power, usually of a fairly low voltage. Typically a minimum of two electrodes are placed within the container. When the liquid reaches a specific point, it will come into contact with the electrodes, completing a circuit and activating an internal switch.
Pneumatic sensors are a relatively cost-effective solution often used for particularly hazardous liquids, or in systems where the use of electricity is not viable or possible. This is because the sensor itself does not come into direct contact with the liquid at all. The sensor detects the level of air between the liquid and the pneumatic sensor and then uses this reading to calculate the amount of liquid used to fill the remainder of the container. These types of liquid level sensors are also relatively cost-effective.
There is a range of liquid level sensors which offer continuous measurement of liquids. Magnetostrictive liquid level sensors are alike in design to regular magnetic float sensors, yet the magnet level is measured using a magnetostrictive wire, which will react when its magnetic field is disrupted by the presence of the magnet. The exact point at which this interruption occurs can be determined by the space between the bottom of the wire and the point of interference.
Alternatives to this design include a magnetoresistive sensor, whereby an additional magnet is inserted into the arm of the float, allowing accurate triangulation of the exact position of the magnets. This type of liquid level sensor is commonly used in conjunction with computer programs due to its accuracy. A non-contact liquid level sensor features advanced signal processing technology to enable non-contact liquid level detection and regulation.
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