Level Transmitters

Level transmitters are devices that measure the level of a solid, liquid or slurry within a container and then convert the information into a comprehensible form. Transmitters are also called sensors or transducers; they both convert signals into a reading of pressure or temperature. There are two main ways level transmitters receive information: by making point level or continuous level readings.

Level Transmitters – Siemens Process Instrumentation

Of the two types of information receiving styles employed by level transmitters, point level transmitters sense when a substance has reached a predetermined level, usually providing an alarm or electrical charge that shuts off the feed. Continuous level transmitters are made up of multiple sensors that provide a constant reading of the level of the substance. These transmitters are small and usually encased in stainless steel for protection because level transmitters are built to withstand a wide range of temperatures, pressures, substances and conditions in the specified space.

This space can be a vat, tank, silo or other container used for mixing, processing or other operations. The transmitters perform an important task because they take measurements where people cannot, like in an enclosed tank or a vat of chemicals with a mixing blade. Knowing how much material is in a container is valuable across many industries because over or under-filling a specified space can lead to hazardous conditions as well as loss of product and time.

Level transmitters use many different methods and technologies to measure the levels of substances. These sensors are unaffected by changes in conductivity, temperature, pressure, humidity or moisture content as well as dust and static-charge buildup. There are five main kinds: non-contacting radar, guided wave radar, ultrasonic, differential pressure and vibrating fork. Non-contacting radar transmitters typically are installed on top of a container, so the waves are sent downward into the enclosure.

The transmitter uses the returning echoes to determine how much substance is in the tank. Guided wave radar transmitters are able to provide both level and interface measurements because the advanced technology can differentiate between different layers of fluids, such as oil and water. Ultrasonic level transmitters have non-contacting sensors housed in watertight enclosures. They use ultrasonic waves to gather information. Differential pressure level transmitters take multiple readings in different places in the container and compare the readings to determine the level.

Vibrating fork transmitters are used with fine powders and granular solids. Multiple tines are lowered down toward the powder and stop when they reach the top of it. They vibrate to minimize material buildup between the probes. Other styles include optical level transmitters, air bubblers and rotation paddle level transmitters.