RADAR-BASED METHOD OF MEASURING THE LEVEL OF A MATERIAL IN A VESSEL

摘要

For measuring the level of a material in a vessel by a radar-based method an antenna arranged above the highest level anticipated radiates electromagnetic waves to the surface of the material contained in the vessel and receives reflected echo waves. The transit time of the wanted echo waves reflected by the material surface is measured from whi ch the level is computed. Since this transit time corresponds to the group delay, for determining the reduction factor by which the group velocity of the electromagnetic waves differs from the velocity of propagation in the free space due to the geometry of the propagation space the phase difference of the wanted echo waves relative to a reference oscillatio n and the group delay are measured for various levels and the reduction factor is determined on the basis of the changes in the phase difference as a function of the group delay.