An Introduction to Radar Sensors

Just like the loudest echo-locating calls of bats – the 80-GHz radar sensors VEGAPULS 6X – can reach up to 120 dB. Image credit: Artem Avetisyan.

Why Does Large Dynamic Range Improve Visibility?

The majority of people would not initially think of the Microchiroptera bat species when providing examples of evolution’s astounding achievements. However, its echo-locating system makes it the best at seeing in the dark out of all mammals, meaning it is more easily able to locate the smallest insects for food.

A similar principle guides the function of radar sensors. The better they can hear their “locating sounds” – or, if we are talking about radar sensors, the greater the dynamics – the more visible the level echo becomes.

In radar level measurement, dynamic range makes the difference. When the view is blocked by build-up and condensation on the antenna, for example, or in poorly reflecting media, the sensor’s dynamic range can provide the required sensitivity in order to detect even the smallest signals reliably.

In this manner, VEGA’s 80 GHz radar sensors, equipped with their uniquely high 120 dB, can achieve a full view under any process conditions.

As it happens, in many bat species, there are significant differences in dynamics. Similar to the VEGAPULS 6X 80 GHz radar sensors, their loudest echo-locating calls can reach as high as 120 dB.

Condensate and Build-Up

Which Media Need an Extra Quantum of Dynamics?

Whether viscous, aqueous, coarse-grained or powdery: A wide variety of liquids and bulk solids ensure reliable supplies of raw materials for production – provided that the operators know the exact filling levels.

Occasionally, though, exact measurement can be extraordinarily difficult. An example of this is when the measured media have a low dielectric constant (DK). Up until now, it was generally understood that a radar or microwave measurement would only function reliably in an obstacle-free tank when the medium had a dielectric constant of 2 or higher.

However, the 80 GHz VEGAPULS 6X radar sensors – courtesy of their unique, high 120 dB dynamics – can detect and measure bulk solids and liquids which have a significantly lower dielectric constant reliably.

This is great news for the following widely used media, among others:

• Polystyrene foam (otherwise called Styropor^®): DK value 1.03
• Plastic powder: DK value from 1.2
• Palm oil: DK value 1.8
• Glass fiber powder: DK value 1.1
• Flax meal, bran, chaff: DK values from 1.3 to 1.5
• Lime and gypsum: DK values 1.5 and 1.8
• Coffee and cocoa beans: DK values 1.5 and 1.8
• Wood chips: DK value 1.1

A further advantage of this is that it is no longer a requirement to search through long DK value lists. This is all courtesy of the VEGAPULS 80-GHz radar sensors with 120 dB.

Why Do These Sensors, with Their High Dynamics, Handle Difficult Measuring Tasks Better?

Image credit: Kaweestudio/Shutterstock

The VEGAPULS 6X 80 GHz radar sensors have an extremely wide dynamic range, allowing them to measure media with poor reflective properties significantly better than standard radar sensors.

These high-frequency measuring instruments, courtesy of their unique 120 dB, are also able to handle extraordinarily difficult measuring situations. These include turbulent product surfaces, foam, and build-up or condensation on the antenna.

How, though, is a measurement application affected by the dynamics? The following 3 facts explain the basics:

1. Decibels or dB are a ‘ratio’ rather than a measure. This ratio explains the power level by comparing two number quantities against each other.
2. dB are logarithmic rather than linear. Consequently, the total value is multiplied exponentially by each additional dB. In practice, this translates as this: an extra 3 dB doubles the power, while the power is increased one million times by an extra 60 dB.
3. The dynamic range in level measurement can be better understood by the following rule of thumb: 26 GHz standard sensors, similar to many 80 GHz sensors, operate with a dynamic range of approximately 90 dB. VEGA’s 80 GHz radar sensors – such as VEGAPULS 6X  – reach up to 120 dB. The dynamic performance is improved 1000-fold by the difference of 30 dB in practice!

It is also worth knowing that the smallest of reflections can be detected by a dynamic range of 120 dB. This makes the measurement of media with low dielectric constants, such as fine-particle silica or polystyrene beads, straightforward.

Why Do Sensors with a Large Dynamic Range Measure Through Glass Vessels and Windows That Much Better?

Image credit: Delpixel / Shutterstock

Let's compare it to sunglasses, which are available with lenses in countless shades – but which one is right for you? If you wish to protect yourself from brighter light sources, you should choose a darker tint of lens, and vice-versa.

Figuratively speaking, lightly tinted lenses are sufficient to deal with a weak light bulb, while you will require significantly darker lenses when faced with a flood-light system.

A standard radar sensor’s “view” when looking through glass is similar to the eye’s view when wearing sunglasses – it is “darkened.” There is a certain dielectric damping factor inherent in glass which has a “darkening” effect on radar.

In effect, glass provides resistance to the microwaves from radar sensors, which are hindered in their transit to and from the surface of the measured medium.

A significant portion of the radar signal is reflected by glass at its surface, and the glass also attenuates it as it passes through. The unfortunate outcome of this is that the remaining emitted radar energy is no longer sufficient for the level that must be measured to be detected reliably by standard radar sensors. This is similar to how weak light sources are unable to penetrate tinted lenses which are too dark.

Why Do These Sensors with High Dynamics Measure Better Through Foam?

While there are numerous 80 GHz radar sensors for level measurement, VEGAPULS is the only one which measures with the high dynamic range of 120 dB. This product offers a head start when measuring applications with foam.

While “dreams are like foam,” bursting quickly like soap bubbles: this is just a saying, foam is surprisingly resistant when one tries to measure through it. This is particularly true of industrial foams, like those found in mining and chemical processes. Those supposedly fragile bubbles in shaving creams and detergents, however, also do a good job, as they are able to weaken measurement signals or completely block them.

Foam’s effect corresponds to the radar sensors’ frequency range: a higher frequency means a shorter radar signal wavelength. A shorter wavelength means the radar signal is more attenuated by the foam.

A 26 GHz radar sensor has a 12 mm wavelength while, in contrast, an 80 GHz radar sensor has a 4 mm wavelength. As a result of the 80 GHz radar sensor’s 3 times smaller wavelength, the radar signal is more strongly attenuated by a factor of 3.

However, in the VEGAPULS 80 GHz radar sensor, the dynamic range offsets this effect. The sensor can, courtesy of its high 120 dB, detect the weaker level measurement signals attenuated by foam more reliably.

In contrast to conventional sensors, which operate with approximately 90 dB, VEGAPULS 6X operates with 120 dB. Consequently, signals are 1000 times larger, and the sensor copes significantly better with foam damping.

Influence of Foam

This information has been sourced, reviewed and adapted from materials provided by VEGA Grieshaber KG.

For more information on this source, please visit VEGA Grieshaber KG.