초록 ▼

A method and apparatus are provided for measuring the level of a surface of a material in a tank. The apparatus and method modulate an optical radiation beam at a radio frequency. The radiation beam is transmitted to the surface and the reflected beam received. The modulation frequency is changed un

A method and apparatus are provided for measuring the level of a surface of a material in a tank. The apparatus and method modulate an optical radiation beam at a radio frequency. The radiation beam is transmitted to the surface and the reflected beam received. The modulation frequency is changed until the phase of the received beam is the same as that from an optical reference path. The optical reference path is any fixed length path that allows the beam to pass from the source of the beam to the receiver that receives the reflected beam. An optical switch determines whether the receiver receives the reflected beam or the reference beam. The change in modulation frequency may then be correlated with the level on the material\s surface in the tank.

대표청구항 ▼

A method of determining the level of a material in a tank, said method comprising the steps of: providing an optical radiation beam and a means for modulating said beam, modulating electrically an optical radiation beam by a radio frequency f, continuously variable over the radio frequency range; tr

A method of determining the level of a material in a tank, said method comprising the steps of: providing an optical radiation beam and a means for modulating said beam, modulating electrically an optical radiation beam by a radio frequency f, continuously variable over the radio frequency range; transmitting said beam to the surface of the material; receiving the beam reflected from said surface; adjusting the modulation frequency in order to obtain phase equality between the modulation in the path in which the beam has travelled to and from the surface and the modulation in a path in which the beam has travelled a preselected fixed distance and generating information indicative of the change in frequency to obtain phase equality; and deriving from the change in frequency information the level in the tank.