| 摘要 |
To measure the height of the surface of a fluent material, such as coal, in a bunker or container, pulsed radiation from a microwave source is beamed down on to said surface, and the return radiation reflected from the surface is processed to detect pulses in the waveform with time-varying amplitudes, and therefore denoting returns from the fluent material, and to reject fixed shape pulses denoting returns from the fixed structure of the bunker. To discriminate between returns of time-varying amplitude (i) from the fluent material surface and (ii) from material flowing in from an in-feed, the higher frequency components, denoting the material flowing in, are filtered out.
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