Level sensors, also known as level indicators, are measurement devices used to determine the level of materials such as liquids, powders, slurries and granular materials. All of these substances have flow, meaning that within containers, they naturally flow to become level due to the effect of gravity.
While they are typically only used to measure materials that flow, level sensors may rarely be used for the measurement of levels for bulk solids. Since maintaining proper levels of materials is essential in many applications, level sensors are often used in industries such as pharmaceutical products production and distribution, for measurement indication of medical ingredients; HVAC, in order to monitor and control the oil or refrigerant level in heating and cooling systems; food and beverage, for monitoring of liquid and powder food items during handling, packaging and processing; industrial manufacturing, to control the levels of potentially hazardous chemicals required in various processing applications; and commercial, for monitoring of liquid levels in many restaurants, office buildings and more.
However, different applications require different types of level sensors and the various criteria that should be used to determine what type of level sensor will be best-suited for a certain application includes temperature, material phase, density, container size and chemistry.
Level sensors typically include a switching mechanism, a tube and a couple of areas of connection. However, the design of the level switch varies widely based on the desired application, and the different factors aforementioned. As a result of those wide-ranging factors, level sensor designs can vary from the simple to the exceedingly complex.
In addition, the level sensors can be triggered by many different conditions including pressure, temperature or buoyancy. Some additional features that more complex level sensors may include are thermal sensors, ultrasonic waves, vibrating sensors and optical sensors. All of these sensors can be modified to recognize specific substances or to reveal when a certain viscosity, density, opacity or thermal conductivity condition is reached.
For construction, level sensor manufacturers typically utilize stainless steel, brass and a couple different types of plastics. Stainless steel is an excellent material choice due to its hygienic properties and high corrosion-resistance, whereas brass works exceptionally well for petroleum-based liquids.
The two most common plastics that are used to fabricate level sensors are polypropylene and polysulfone. These two plastics offer advantages such as availability in different colors, good choices for acidic conditions such as in electroplating and metal cleaning as well as lower-temperature food processing applications.