One of major characteristics of any radar level transmitter, which affects most performance parameters (measuring accuracy, measurement constancy, sensitivity), is the width of a measuring beam.
The level probe installed on the tank roof emits electromagnetic waves – a measuring beam – having an expanding radiation pattern towards the monitored product.
Such a radiation structure exists due to fundamental physical laws. As an analogy, we can refer to an electric torch: the farther from it the illuminated surface and the smaller its reflector (“antenna”) diameter, the larger the torch light spot. The only reason we see this light spot is that the reflecting light falls into our eyes (“receiver”). A very similar principle acts in case of electromagnetic microwaves. An electromagnetic wave radiates towards the product, reflects from it, and returns into the antenna of the level transmitter's level probe.
The measuring beam width is characterized by a beam divergence angle. The wider the beam (the larger the divergence angle), the lower percentage of the emitted signal (all other conditions being equal) that will return to the receiver of the level transmitter's probe to “bring” information on the tank filling level. That is, the narrower the measuring beam of the level transmitter, the more sensitive the level transmitter. Therefore, a narrower beam can ensure significantly higher level-measurement quality a larger installed height (i.e. a higher tank) makes this effect more pronounced and better improves the quality of the level transmitter's operation. The measuring beam width of the ULM-11 level transmitter is 40.
The narrower the beam, the easier installation of the level transmitter on the tank. The level transmitter's probe can be located closer to the tank wall it is easier to select the installation place so that to prevent foreign objects and tank structure elements from blocking measurement.
Foreign objects and tank structure elements on the measuring-beam path result in additional interference and, therefore, a more probable increase of the measurement error and more likely situations with unstable measurements.
Thus, the level transmitter with a narrower beam is a more versatile level-measurement instrument than that with a wider beam.
A smaller beam width can be ensured by a larger antenna diameter of the level transmitter's probe and a higher frequency of the emitted electromagnetic signal. For instance, the ULM-11 level transmitter operates at a frequency of 94GHz and has the measuring beam width of 40 at the antenna diameter of 86mm. Up to date, only our company possesses a manufacturing technology of radar level transmitters operating at this frequency.
Other manufacturers have to achieve similar characteristics of the beam divergence angle (60–100) at the level transmitter's operating frequency of 10– 24GHz by increasing the antenna diameter.
The product range of ULM level transmitters includes various level-transmitter modifications, with different metrological and performance characteristics. Therefore, the most optimal solution in terms of a price/quality ratio can be selected for most of level-measurement tasks.