| 摘要 |
A method and a device for measuring, by means of radar, in an enclosed space (1) in which a liquid (2) is stored, the level of a liquid surface (6), where the method involves the steps: a radar unit (3) mounted on the roof (4) of the enclosed space transmits a microwave signal downwards into the enclosed space (1) through a waveguide (7) that communicates with the liquid in the enclosed space; the transmitted microwave signal's polarization alters according to a predetermined time sequence in such a way that the signal is propagated alternately at least in a first and a second plane of polarization; the signal transmitted in the first plane of polarization is reflected by the liquid surface (6) back to the radar unit (3); the signal in the second plane of polarization is reflected by at least one reference transmitter placed at a known distance from the radar unit; a calculating unit calculates the level of the liquid surface based partly on the propagation time for the microwave signal, i.e. for the time between the signals emitted and received by the radar unit, partly on the microwave signal's velocity of propagation, which is obtained from measurements in relation to the references.
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