Most dry chemical storage silos utilize the guided wave radar method of level measurement. This means that a radar probe is suspended by a rope from the transmitter on the roof of the silo, to the point where the main silo section meets the cone. The radar probe does not extend all the way into the cone and usually only measures product level in the cylindrical portion of the silo. Depending on the product being stored and the size of the silo, the ‘unmeasured’ cone section of the silo may account for a significant amount of the storage capacity.
This issue can be addressed by having an appropriate offset in the calibration of the instrument.