The article takes on non-contact radar level transmitters, also known as free space radars. Yep, same device, just a different name. They have various frequency range options as well, and this article will help you decide which non-contact radar level transmitter frequency range you need.
Time of Flight
Time of flight means the time it takes the radar signal to reach the surface of your product and return. Radar uses electromagnetic waves, while ultrasonics use mechanical waves.
To know more about it, you can read our article on time of flight (ToF)
Radar level transmitters have a number of frequency range options. You can have 6 gigahertz (GHz), 26, and more. But why all the frequencies, and which one will work for your application?
Take a seat and find out the differences between the types of frequency ranges. In fact, you’ll also find different sales pitches for these bands, depending on the company.
So we’ll analyze these differences and see what happens!
Radar level transmitter frequency ranges
So many frequencies, so little time! You’ll need to pay attention to how they differ to find one to suit your needs. Military radars use a specific frequency range, as do satellites, so you may have to factor communication into your requirements too.
For example, radar gun frequency ranges change from country to country. The first generation of radar guns used a frequency range from 8 to 12 GHz called the X band. The new generation of radar guns use the K band (18 to 27 GHz), and you can find radar level transmitters using Ka-Band (27 t0 40 GHz).
Radar level transmitters on the market come in four different frequencies. You have radars based on C band (6 GHz), K band (26 GHz), and X band (10 GHz). Then some vendors produce radars on the W band (75-85 GHz). And here comes the drama! Beware the terror of – misalignment!
Vendors who offer W-band radar transmitters have rainbows and kittens in their sales pitches. And companies who don’t will throw tomes of technical explanations at you about why you need to stick to the other bands. We’ll go through this topic later.
If you read our reviews of the Pulsar R96 and the SITRANS LR200 or their comparison, we mentioned beam angle and beam spread. You need these details to fit a radar level transmitter for your application.
For instance, you can’t use radar level measurement in a tank with an agitator if you have low dielectric constant. The signal will reflect off of it and give a bad reading, however, you have exceptions on the market.
So the beam angle and spread have to do with your radar level transmitter’s antenna and frequency range. A low-frequency radar with a common antenna will have a beam angle around 20 degrees. For example, the SITRANS LR200 works with 6 GHz. A 4-inch antenna creates a beam angle of 29 degrees, and an 8-inch antenna has a beam angle of 17 degrees.
The VEGAPULS 62 works on 26 GHz, so you can have a beam angle between 8 and 22 degrees. So you see that higher frequencies can have lower beam angles using small antennas. You can get lower beam angles with low-frequency radar transmitter, but you need big antennas, often too big for common processes.
So you get why big antennas don’t work, but why small beam angles? It means that the radar can measure in low tanks, or tanks with interference, or even close to the tank wall.
Endress+Hauser also offers high-gigahertz technology, with options for process and storage applications. The reps say 113 GHz, but that’s just a sum of the frequencies, so don’t get too impressed.
Low or high radar level transmitter frequency range?
Different manufacturers have different views and standpoints in this regard.VEGA and Endress+Hauser sell positive messages for high-frequency radar.
Emerson starts with interference, saying that high-frequency radar devices have problems with vapor, foam, or buildup.
VEGA and Endress+Hauser have countered these arguments with videos and recommendations for stilling wells and bypasses.
What radar level transmitter frequency range should I choose?
Radar level measurement has come a long way since its introduction 40 years ago and the technology will continue to develop and improve. The recently introduced radars using the 75–85 GHz frequency range may have benefits in level measurement applications for very small tanks with small process connections and very short measuring ranges. However, the fundamental suitability of 6–11 and 24–29 GHz frequencies for reliable mm-accuracy level measurement cannot be overlooked. High-frequency technology will usually perform well in less challenging process conditions, but fundamental microwave physics shows us it is less suitable when the going gets tough. In contrast, low and mid-frequency technology was developed specifically to meet the toughest level measurement challenges in the most demanding industrial applications. And the reason these instruments have been such an incredible success is that they provide reliable and accurate measurements in almost all applications.
Now you can select the radar level transmitter frequency range of your dreams using your process requirements. Don’t forget to check the accuracy and benefits for your application and to analyze the prices and local support, which all factor into which will be the perfect device for you.
Still confused about radar level transmitter frequency range? Get in touch with our engineers!