The use of the radar level transmitter for the process industry started back in 1991. These were extremely large units and operated with a 6GHz frequency. The units were sold generally into liquid applications and were only ever considered when no other technology would work. They were a large unit weighing in at several kilograms and operated only from an AC supply.
In 1997 Vega released the world’s first true loop powered radar level transmitter, offering a more suitable transmitter for typical process applications. But once again they came with their limitations. 1999 saw the 26 GHz radar level transmitter being released, offering a smaller unit with a reduced antenna size and narrower beam angle (a downside to lower frequencies is the larger beam angle).
Vega continued to develop and improve radar level transmitter performances through the first decade of 2000. The main changes were in the software area where, thanks to customer feedback, the parameters for setup were improved and made much more descriptive and user friendly.
As with all developments you reach a point where the components and physics of the technology have been maximised. At this stage, Vega started research on the 80 GHz frequency range. This frequency was not new to the market as it was and still is quite common in the automotive industry with reversing sensors.
During the research and development of this frequency Vega carried out a number of real-life customer trials and the results of these opened up many more opportunities for the use of the radar that had never been practical before. It also allowed, for the first time, antenna sizing and adaption to many typical process fittings that exist in the industry. One of the things to note with regard to radar frequencies is that, as you increase the frequency, the antenna size and the beam angle reduce.
Radar level transmitters work on the reflection of the signal from the product being measured, and the strength of that returned signal is based in the Dielectric Constant (conductivity). So, in the past, they were not considered suitable for applications that have a relatively low DK value radar. 80 GHz now allowed these measurements to take place, but, of course, there are other considerations.
As well as the high frequency, you also need quality components that provie you very good sensitivity or dynamic range as it is commonly known as. Typically, up to this point, radar level transmitters had a dynamic range of around 90 db – that is, until the VEGAPULS 64 (liquids) and the VEGAPULS 69 (solids) were developed. Vega had manufactured a radar level transmitter with a dynamic range of 120 db. So what does this mean? Well, as with audio, for every increase of 3 db you get a doubling of the power. An increase of 30 db over the previous and existing radar frequencies achieve an increase of over 1000 times in the sensitivity of the Vega 80GHz radar level transmitters. For this increase Vega transmitters were now able to measure extremely low DK products such as plastics.
Radar level transmitters, like all instruments, do have their limitations, and many limitations are set by the physics of the technology. It is very important to take into account not just the frequency, but all the data, when evaluating whether a transmitter is suitable for the application. At Vega, 80 GHz has proven to be a large step forward in solving difficult applications, but the company has developed a model for liquid applications and a model for solids applications, as different algorithms for the types of process medium are needed.
Radar level transmitters are now a very accepted form of non-contact level measurement and the use of these units has increased by many times over the past decade. But as with all developments, this one has not yet finished, and Vega is continuing to improve the transmitters. The company said that, in the near future, it will again break through barriers and open up opportunities for radar to provide more solutions in industry applications.