Radar measures the level of material by monitoring the time it takes for a microwave pulse to travel from the level meter to the surface of the material being measured and back to the meter. The time is calculated into distance which is then translated into a level measurement.
Radar operates at various frequencies that normally range from 5.8 GHz up to 78 GHz. Frequency is the number of transmitting cycles per unit of time and is measured in hertz. Higher frequencies move at faster intervals and allow for a narrower beam angle. On the other hand, lower frequencies will have a larger width of the beam angle for a given size of antenna. The lower the frequency, the less sensitive the device will be to dusty conditions inside of a tank or silo. The optimal level of frequency for a radar device will vary from application to application. To find out if radar technology is suitable for your application, be sure that technical specifications are reviewed and an application data sheet is completed.
An antenna is used to direct the beam angle to an optimal position in the material to get an accurate level measurement reading. A narrower beam angle allows the unit to focus on a particular point of the material and see past obstructions in the tank or vessel. By being able to see past obstructions, such as a split silo construction or a silo with internal baffles or welds, the radar unit will give more accurate readings. A narrower beam angle is also better for sharper angles of repose. A wider beam angle is more forgiving when false echoes from the internal structure of a vessel or silo cannot be avoided. Wider beam angles are effective for high levels of dust or steam.
Frequency and beam angles are important factors in gaining the most accurate measurements of dry bulk materials in vessels such as silos.