Electricity + Control

The introduction of 80 GHz radar sensors represents a paradigm shift in liquid level measurement. High-frequency devices have ushered in an era of new possibilities for the process control industry, and it’s all because of signal focusing. Let’s look at all the things an 80 GHz radar sensor can do.

Focused beam avoids obstructions

Increased focus of the beam angle is the principal benefit of 80 GHz radar instruments; the one improvement that makes all the rest possible. In every process, focus is crucial to accurate level measurement, and these new instruments emit the most focused signals on the market.

Tank PS64 028The focused beam (yellow) of 80 GHz radar sensors avoid internal agitators that contact the 26 GHz radar beam (gray).

Plant operators have struggled with unfocused radar for decades—particularly in liquid level applications. The wide beam angle of 26 GHz sensors (and 6 GHz sensors before them) made it difficult for radar signals to miss agitators, heating coils, and other vessel internals. For example, a radar sensor with a transmission frequency of 26 GHz and an 80 mm-diameter antenna was limited to a beam angle of approximately 10°. These instruments picked up reflections from vessel installations that distorted the returning signal, forcing users to make adjustments to monitor the true liquid level.

With an antenna of the same size, 80 GHz gauges emit a beam angle of only 3°. This allows them to be used in vessels with internal installations or heavy build-up on the walls; the focused microwave beam simply avoids these obstacles as if they aren’t even there. This is welcome news in chemical and food production, where obtrusive internals are the norm and space is at a premium.

Photo VEGAPULS64 023Small process fittings make 80 GHz radar sensors ideal for retrofitting onto existing tanks.

An exciting benefit of increased signal focusing is the performance of 80 GHz radar sensors when mounted on ball valves. Historically, attaching a 26 GHz radar gauge to a ball valve and receiving an accurate level measurement has been a significant challenge. Ball valves contain many interior surfaces that reflect radar signals. To make matters worse, they are often used in combination with a bleed ring that can create even more signal noise. All of these reflections make it difficult to discern which signals are generated by the valve and which are from the product. This confusion forces operators to turn to instrumentation manufacturers for help, but the best solutions are often difficult to implement and may require periods of trial and error despite the best efforts of plant technicians. Before long, the manufacturer’s tech is on site servicing the 26 GHz radar.

The increased focus of high-frequency gauges means fewer signals are reflected by the valve’s interior. This minimized noise creates a clear picture of the level inside a tank. Users across the world have experienced consistent level measurement mounting an 80 GHz radar gauge on garden-variety 3-inch and 4-inch ball valves. The bigger the valve, the clearer the signal, but 80 GHz sensors are also performing well on 2-inch ball valves. This is a big break for users who need ball valves to separate their equipment from their product but have avoided installing a radar level device because the degree of measurement difficulty was too great. Radar’s accuracy and low-maintenance reliability is now a viable option.

Superior focus makes for accurate measurement without adjustment even when mounted on a ball valve, but the increased focus of 80 GHz radar sensors creates other benefits for users.

Small antennas take radar where radar has never gone before

Amping up a radar sensor’s focus has an opposite effect on it’s antenna—it’s size decreases as transmission frequency increases. An 80 GHz sensor, therefore, does not require a large horn to focus it’s beam at the measured material. The signals take a narrow beam all on their own. The saved space makes a huge impact, particularly as it applies to retrofitting. Plants can now integrate the most advanced radar devices into an existing process without shelling out thousands for vessel modifications. For users who have longed to use radar but could not afford a retrofit, this news is tantamount to a budget increase. Smaller instruments, however, aren’t just good for old vessels; they can also help manufacturers stay nimble and market-responsive.

There’s a trend in the pharmaceutical and chemical industries toward batch production. Batching allows operators to produce seasonal and low-volume products with less financial investment. Small batches are produced in small vessels, where conventional wisdom says using radar is impossible due to small process connections. Thanks to the compact antenna of 80 GHz radar sensors, that is no longer true, and operators no longer have to sacrifice accurate measurement in the name of space.

Enhanced resolution measures to the last drop

Any fan of cliché action films is familiar with this scene: An investigator stands behind a computer whiz in a laboratory full of expensive-looking surveillance equipment. They are watching a grainy piece of closed-circuit video, knowing that one of the pixelated figures on the screen is a criminal mastermind. The computer whiz punches a few keys and the word ‘Enhance’ appears in green letters on the computer screen. The blurry face gets a little clearer. The computer whiz clacks away at the keyboard and “enhances” the footage once more, revealing a crystal-clear image of the villain’s face. This might be an example of lazy screenwriting, but it’s a good analogy for the difference in resolution one would experience when switching from low-frequency to high-frequency radar sensors.

When the level of liquid in a vessel gets low enough, 26 GHz radar is unable to distinguish the signal returned by the remaining product from that of the tank bottom, and the user rightly thinks the vessel is empty when it isn’t. This is the same as the action-movie computer whiz being unable to “enhance” surveillance footage. Limited resolution presents a natural handicap to process efficiency. Ultra-focused 80 GHz devices measure liquid down to the last millimeter in the tank, giving users accurate data they can use to optimize their processes. It won’t thwart a terrorist attack or prevent an elaborate heist, but the enhanced resolution of 80 GHz radars sensors helps users avoid waste.

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Email: ec@crown.co.za
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Email: helencou@crown.co.za
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Phone: +27 11 622-4770
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