Level Measurement & Control


Understanding dynamic range and the versatile future of radar technology

August 2016 Level Measurement & Control

Radar technology is a vastly popular means of process instrumentation. From grain silos to oil refineries to chemical facilities, radar is trusted to keep processes running at maximum efficiency. As products and processes have grown more complex over time, radar technology has adapted to keep pace with market demands. One of the ways these instruments have advanced is by increasing the dynamic range. This paper explains dynamic range and its importance in solid and liquid applications.

Dynamic range vital to level instrumentation versatility

Large dynamic range allows radar technology to accurately measure liquids and solids in a variety of applications. Measured in decibels (dB), dynamic range (also called dynamics) is an indicator of sensitivity; it refers to the range of usable signals a device can detect. The larger the dynamic range of radar instrument, the smaller the signals it can measure in operation, and the more useful it is to multiple industries.

To gain a conceptual understanding of dynamic range, consider two common types of scales found at home. A standard digital bathroom scale measures weights up to 330 pounds (150 kg) and does so in 0,2 lbs (0,1 kg) increments. Considering 0.2 lbs. is a small value and 330 lbs. is quite heavy, it is safe to say that a bathroom scale has good range. Moving to the kitchen, we would find that the produce scale has good range as well. Granted, the typical produce scale only measures up to 44 pounds (20 kg), but it does so in two ounce (55 g) intervals. Each scale is limited to a set range of weights it can measure, and we can compare the size of those ranges.

Just as with radar instruments, the value of a scale’s range differs depending on application. A dieter depends on the range of a produce scale to weigh in ounces (grams) the blueberries he eats for breakfast. He also depends on the range of the bathroom scale to measure in tens of hundreds of pounds (kilograms) the effects of his healthy diet. Substituting one scale for the other will not give the dieter accurate data and would likely result in a bathroom full of blueberries and the busted remains of the produce scale scattered across the kitchen floor. No one wants that.

Now, imagine a radar level device with the dynamic range of 96 dB is a bathroom scale. After weighing in, you could step off the scale, remove one hair and step back on, and the scale would detect the difference. That is amazing, but 96 dB is hardly the top of the mountain when it comes to the dynamics of modern radar instruments. Many level devices offer a dynamic range of 120 dBs. If one of these units were a scale, you park a truck on it and remove a hair, and the scale would furnish a lighter weight. The market’s most technologically-advanced radar devices have a dynamic range of 128 dB. Applying those dynamics to a scale, you could do the hair trick while sitting in a train, and the scale would show the difference. Installing these radar devices in a plant is the equivalent of owning a home scale that reaches the light end of the produce scale’s range, the heavy end of the bathroom scale’s range, and far, far beyond.

For example, let us compare the first and last devices in our analogy. The 24 dB difference in dynamic range corresponds to our factor of 200. This means signals appear 200 times larger in the 120 dB instruments than they do in the 96 dB instrument. The 8 dB difference between the second and third radar device also represents a large chasm in performance than one might assume, as 8 dB corresponds to a factor of five. The incredible sensitivity is an important feature to plant operations in various industries.

Dynamic range in demand for measuring difficult media

The need for radar sensors with large dynamic range, changes based on the media being measured. Power plant operators rely on radar sensors to detect the height of coal stockpiles and to control the position of conveyor belts that feed product to the pile. In this application, a sensor does not need large dynamics because coal is highly reflective of radar signals, so a device with small dynamic range will work just fine. This is not the case for media with poor reflective properties.

The chemical industry, for example, is thick with solids and liquids that do not easily reflect radar signals due to low dielectric constant (dK). These low-dK materials demand a radar instrument that performs more like a produce scale than a bathroom scale to detect their miniscule signals. In other words, they require a radar instrument with large dynamics. Radar sensors with dynamic range of 120 dB can measure any liquid: In fact, it is safe to say the days of looking up dK values are over. However, chemical composition is not the only reason to choose a sensor with large dynamics to measure process liquids.

Dynamic range helps a radar sensor perform in difficult conditions. For instance, foaming runs rampant in chemical vessels that use an agitator to mix or dissolve liquid product. Operators hesitate to use radar instruments in these applications because foam attenuates radar signals. In extreme cases, foam can completely absorb radar signals and prevent them from returning to the sensors. However, radar devices equipped with large dynamic range compensate for foam with greater signal strength than their predecessors. By emitting a stronger signal to the liquid, modern sensors detect the small signals that make it back through the foam. The Vegapuls 64, VEGA’s new liquid level measurement device, is such a radar sensor.

Conclusion

Dynamic range of a radar device refers to its sensitivity to – and ability to measure – small signals. Process instrumentation manufactures are responding to the growing demand for large dynamic range by bringing to market radar devices that accurately measure increasingly difficult media. The result is greater application versatility. Radar is now a viable technology in industries that previously ruled it out, giving plant operators a new, reliable option for process measurement.

For more information contact Chantal Groom, VEGA Controls SA, +27 (0)11 795 3249, chantal.groom@vega.com, www.vega.com



Credit(s)



Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

VEGA handles the pressures of water treatment systems
VEGA Controls SA Pressure Measurement & Control
A water treatment system for a major metropolitan area in the Midwestern United States demands careful monitoring and management of processes across its sprawling network. Choosing VEGA for its process automation needs meant more than just obtaining precise and reliable pressure sensors.

Read more...
Cloud-based inventory management software
Endress+Hauser South Africa Level Measurement & Control
Netilion is an award-winning cloud-based IIoT ecosystem designed for industrial processes. It connects the physical and digital worlds to send valuable information from the field straight to your phone, tablet or other device.

Read more...
Sensor technology for cartonboard machine for paper and packaging
VEGA Controls SA Pressure Measurement & Control
Paper and packaging specialist, LEIPA undertook a comprehensive modernisation project, combining three stock preparation lines into one, and making investments in new plant components and extensive automation technology. Because of the good experiences the company had already had with VEGA sensors, those responsible for planning and maintenance decided in favour of the VEGABAR 82 pressure transmitter as the standard instrument for level and pressure measurement in the new stock preparation system.

Read more...
Level sensing, conveyor control and grid resistors
DRH Components Editor's Choice Level Measurement & Control
DRH Components is a specialist electric component and systems supplier with a focus on the control of electric motors. As part of its wide variety of products, the company markets the entire Bindicator range. Bindicator manufactures sensors for dry bulk and liquid level measurement.

Read more...
Level measurement under extreme plant processing conditions
VEGA Controls SA Level Measurement & Control
Level measurement in LNG and LPG processes is about answering the simple question: “How much product is in the tank?” However, obtaining an exact value is not easy. The products are often under pressure, cryogenic, and highly explosive. Sensors from Vega have been operating successfully in all stages of the LNG/LPG process for many years.

Read more...
Process measurement solution for Copper Belt’s Kansanshi Mine
VEGA Controls SA Pressure Measurement & Control
Kansanshi Mine faced measurement challenges in its gland water tanks, slurry, and raw materials in the stockpiles and crusher bins. VEGA was able to offer a suitable solution to resolve these challenges.

Read more...
Grounding of hydrostatic level sensors
WIKA Instruments Level Measurement & Control
Hydrostatic level sensors are very often installed in outdoor applications, primarily in the water and wastewater industries. A good connection to ground is essential when installing hydrostatic level sensors, since no grounding or poor grounding can result in destruction or damage to the level sensor.

Read more...
Pressure and level switches for food production
VEGA Controls SA Pressure Measurement & Control
New compact measuring instruments from VEGA prove that automation in food production can be very simple and economical without compromising on hygiene or safety.

Read more...
The dream team for heat and condensate
VEGA Controls SA Pressure Measurement & Control
Meeting the highest safety standards in all process steps is an indispensable requirement in the chemical industry. VEGA electronic differential pressure measuring systems provide perfect safety with the innovative combination of ceramic and metallic measuring cells.

Read more...
VEGA expands radar portfolio for factory automation
VEGA Controls SA Editor's Choice Level Measurement & Control
VEGA is known worldwide for ensuring safe and stable processes with its level and pressure sensors, even under the most difficult conditions. The world market leader is now putting the finishing touches to its radar level portfolio, especially to meet the demands of fast processes in factory automation.

Read more...