Level Transmitters measure the level of a variety of materials, including water, other liquids, bulk solids, and powders. The Level Transmitter provides a continuous electrical output interpreted by a measurement or control system connected to it. Applications for Level Transmitters include material handling, chemical process plants, water treatment plants, and the food and beverage industry. In an industrial setting, it is often critical to know the amount of material you have in a tank to ensure your industrial process's safety and cost-effectiveness. Because you: - Don't want to run out of material - Do you want to avoid a tank overfill incident (hazardous spill) - Need to know the rate of material consumption to optimize your process. There are three main ways that Level Transmitters measure level: - Weight of a material - Pressure Head of a fluid - Position of material within a container
LIQUID LEVEL TRANSMITTERS The liquid Level Transmitter communicates the pressure head of a liquid. This pressure head is used to calculate the liquid's height based on the density of the liquid and the tank's geometry. Typical applications include storage tanks for water and other liquids, and transportation tanks. Advantages include: easy to set up, available in materials robust against most environments. MAGNETIC LEVEL TRANSMITTERS As the title indicates, this type of Level Transmitter tracks the position of a magnet. The magnet is embedded in a float that tracks the surface of the liquid. The float is traditionally constrained from lateral movements in a standpipe connected to the main tank. The output of the magnetic Level Transmitter changes with the magnet's position, which is changing with the liquid level. Note: the standpipe and float must be constructed of a non-magnetic (magnetically transparent) material for proper operation. Advantages include: easy to install or retrofit, and simple electrical connections. CAPACITANCE LEVEL TRANSMITTERS Capacitance Level Transmitters have two or more electrodes. These electrodes (conductive plates) are immersed in a dielectric liquid in the tank. The liquid's dialectic constant must be known for this technique—the capacitance changes as a function of the liquid level. Therefore the liquid level can be calculated by transmitting the capacitance. Advantages include accuracy independent of fluid movement, simplicity (no moving parts), and low maintenance. HYDROSTATIC LEVEL TRANSMITTERS This Level Transmitter type uses the pressure head produced by the liquid to create a variable electrical output. The pressure level can then be calculated by knowing the liquid's density and the geometry of the tank. Advantages include: fits into pipes, robust, reliable, and simple to install. RADAR LEVEL TRANSMITTERS In this application, a radar beam is typically shot from above to the surface of a liquid. The time it takes for the radar pulse to hit the liquid and return indicates the liquid level. Advantages include: easy to install and service, accurate readings, and minimal contact with the measured material. ULTRASONIC LEVEL TRANSMITTERS For an ultrasonic Level Transmitter, an ultrasonic pulse is shot from above to the liquid's surface. The time interval for the ultrasonic pulse to hit the liquid and return tells you the liquid level. Note: gases above the liquid may impact the time interval of the ultrasonic pulse. Advantages include minimal contact with the material being measured. MICROWAVE LEVEL TRANSMITTERS The microwave Level Transmitter sends a microwave pulse through a sensor cable or rod to the liquid's surface. The time is taken to go out and come back directly correlates to the liquid level. Advantages include minimal contact with the material being measured,
Level Transmitters fall within two main classifications—direct and indirect measurement. - Direct measurement is when the actual level of material is measured; whereas - Indirect measurement provides the measurement by way of - Tracking a magnetic structure floating on the liquid, or - A calculation, e.g., the pressure head, indicates fluid height when the fluid and tank geometry properties are known.
