Abstract: A method includes transmitting wireless signals towards a material in a tank and receiving wireless signals reflected off the material. The method also includes calculating a phase velocity of the wireless signals reflected off the material and identifying a level of the material in the tank using the phase velocity. Calculating the phase velocity of the wireless signals could include identifying a plurality of linearly-spaced frequencies and performing linear interpolation using the data identifying the wireless signals to identify data points at the linearly-spaced frequencies. The identification of the data points at the linearly-spaced frequencies could represent the only interpolation operation performed during the calculation of the phase velocity and the identification of the level of the material. Moreover, a mismatch could exist between an inner diameter of a stillpipe through which the wireless signals are transmitted and a diameter of an antenna used to receive the wireless signals.

Abstract: A method includes retrieving at least one first measurement associated with material in a tank from a memory at a level gauge. The method also includes comparing the at least one first measurement to at least one second measurement associated with the material in the tank. The method further includes determining whether a difference between the at least one first measurement and the at least one second measurement exceeds a threshold. In addition, the method includes identifying a current level of the material in the tank in a first manner if the difference does not exceed the threshold or a second manner if the difference does exceed the threshold. The first manner could include correcting a level measurement using the difference between the at least one first measurement and the at least one second measurement. The second manner could include identifying an offset value based on differences between pairs of level measurements.

Abstract: A method includes lowering a sensor unit in a tank, where the tank is capable of receiving a material. The method also includes determining a first distance between the material and the sensor unit and determining a second distance between the sensor unit and a main unit that lowers the sensor unit. In addition, the method includes determining a level of the material in the tank using the first and second distances. The method could further include calibrating the sensor unit to compensate for variations in a medium within the tank, where the sensor unit transmits wireless signals through the medium to determine the first distance. Determining the first distance could include using an ultrasonic measurement technique, and determining the second distance could include using a non-contact servo measurement technique.