Siemens Ultrasonic Level - How it Works

Ultrasonic level measurement is a highly cost-effective solution for short- and long-range measurement, even under difficult environmental conditions such as vibrations and dust. Ultrasonic level measurement is a non-contacting technology used in numerous industrial areas to monitor and control the level of liquids, slurries and solids.

Watch the video below for a better understanding of how this technology works.

For more information on Siemens ultrasonic level measurement, contact Ives Equipment by calling (877) 768-1600 or visiting http://www.ivesequipment.com.

A Proven Ultrasonic Level Transmitter for Environmental, Water/Wastewater, and Energy Management Industries

Reliable level control for
environmental applications
SITRANS LU150/180

The SIEMENS SITRANS LU150 is a short-range general purpose, 2 wire, 4 to 20 mA loop powered transmitter ideal for liquids, slurries, and bulk materials in open or closed vessels to 5 m (16.4 ft). The SITRANS LU180 is the intrinsically safe model.

Designed primarily for liquid applications in the environmental, water/wastewater, and energy management industries, the device is ideal for non-contact continuous level measurement of liquids and slurries in open or closed vessels.

The reliability of the level readings are based on Sonic Intelligence echo processing algorithms that Siemens has been refining for decades. These algorithms differentiate the true material level echoes from the false ones that can result from acoustic or electrical noises, as well as from agitator blades in motion. It's effective, accurate, unique, and it's exclusively Siemens.

Key Applications

• Chemical storage vessels 
• Filter beds
• Mud pits
• Liquid storage vessels 
• Food applications

For more detailed information, check out the brochure below:

A Proven Ultrasonic Level Transmitter for Environmental, Water/Wastewater, and Energy Management Industries - The SITRANS LU150 & LU180 from Ives Equipment

HydroRanger 200 Customer Loyalty Offer from Siemens

Take advantage of this
offer for the HydroRanger200

Time sensitive post!

Siemens Process Industries & Drives Division is pleased to bring you the enhanced HydroRanger 200 HMI ultrasonic level controller for measurement in a wide range of industrial applications including water/wastewater monitoring and pumping, inventory management, truck load-outs, and open channel monitoring.

Enhancements include faster commissioning with an improved HMI (Human Machine Interface) and graphical Quick Start Wizards as well as a redesigned enclosure with removable terminal blocks and wider communications.

The HydroRanger 200 HMI provides high performance measurement of level, flow, differential level, and volume conversion, with additional alarm and pump control functions. Siemens’ patented Sonic Intelligence signal processing technology differentiates between true and false echoes from obstructions or electrical noise, giving users repeatable, fast, and reliable measurements.

Siemens is making it easy for you to see the benefits this instrument has to offer. As a loyal customer, they are offering you a 15% discount toward the purchase of the enhanced HydroRanger(s) 200 HMI version.

Call Ives Equipment at 877-768-1600 to place your order.
Use discount code: SPR6029
(Offer valid until December 31, 2016).

Ultrasonic Level Measurement

Ultrasonic level instruments measure the distance from the transmitter (located at some high point) to the surface of a process material located farther below using reflected sound waves. The frequency of these waves extend beyond the range of human hearing, which is why they are called ultrasonic. The time-of-flight for a sound pulse indicates this distance, and is interpreted by the transmitter electronics as process level. These transmitters may output a signal corresponding either to the fullness of the vessel (fillage) or the amount of empty space remaining at the top of a vessel (ullage).

Ullage is the “natural” mode of measurement for this sort of level instrument, because the sound wave’s time-of-flight is a direct function of how much empty space exists between the liquid surface and the top of the vessel. Total tank height will always be the sum of fillage and ullage, though. If the ultrasonic level transmitter is programmed with the vessel’s total height, it may calculate fillage via simple subtraction:

Fillage = Total height − Ullage

If a sound wave encounters a sudden change in material density, some of that wave’s energy will be reflected in the form of another wave in the opposite direction. In other words, the sound wave will “echo” when it reaches a discontinuity in density20. This is the basis of all ultrasonic ranging devices. Thus, in order for an ultrasonic level transmitter to function reliably, the difference in densities at the interface between liquid and gas must be large. Distinct interfaces of liquid and gas almost always exhibit huge differences in density, and so are relatively easy to detect using ultrasonic waves. Liquids with a heavy layer of foam floating on top are more difficult, since the foam is less dense than the liquid, but considerably denser than the gas above.

A weak echo will be generated at the interface of foam and gas, and another generated at the interface of liquid and foam, with the foam acting to scatter and dissipate much of the second echo’s energy.

The instrument itself consists of an electronics module containing all the power, computation, and signal processing circuits; plus an ultrasonic transducer to send and receive the sound waves. This transducer is typically piezoelectric in nature, being the equivalent of a very high-frequency audio speaker.

The ISA-standard designations for each component would be “LT” (level transmitter) for the electronics module and “LE” (level element) for the transducer, respectively. Even though we call the device responsible for transmitting and receiving the sound waves a transducer (in the scientific sense of the word), its function as a process instrument is to be the primary sensing element for the level measurement system, and therefore it is more properly designated a “level element” (LE).

This photograph shows a typical installation for an ultrasonic level-sensing element (LE), here sensing the level of wastewater in an open channel:

If the ultrasonic transducer is rugged enough, and the process vessel sufficiently free of sludge and other sound-damping materials accumulating at the vessel bottom, the transducer may be mounted at the bottom of the vessel, bouncing sound waves off the liquid surface through the liquid itself rather than through the vapor space. As stated previously, any significant difference in material densities is sufficient to reflect a sound wave. This being the case, it shouldn’t matter which material the incident sound wave propagates through first:

This arrangement makes fillage the natural measurement, and ullage a derived measurement (calculated by subtraction from total vessel height).

Ullage = Total height − Fillage

As mentioned previously, the calibration of an ultrasonic level transmitter depends on the speed of sound through the medium between the transducer and the interface. For top-mounted transducers, this is the speed of sound through the air (or vapor) over the liquid, since this is the medium through which the incident and reflected wave travel time is measured. For bottom-mounted transducers, this is the speed of sound through the liquid. In either case, to ensure good accuracy, one must make sure the speed of sound through the “timed” travel path remains reasonably constant (or else compensate for changes in the speed of sound through that medium by use of temperature or pressure measurements and a compensating algorithm).

For more information, check out this online document or visit Ives Equipment at www.ivesequipment.com.

SIEMENS MultiRanger 200 from Ives Equipment

(Attribution to Tony R. Kuphaldt under Creative Commons Attribution 3.0 United States License)