| 摘要 |
<p>A method of measuring the height of the cutting table of an agricultural implement relative to a surface of the ground with crops by means of an acoustic transducer (2). The sound signal emitted by the transducer (2) is formed by a pseudonoise signal covering a predetermined frequency band. The sound signal is compared with the reflected signal, and the signals are mutually delayed until the comparison has reached its optimum. The delay represents then a measurement of the distance to the surface of the ground. In this manner only the signals originating from the reflection from the surface of the ground are measured, as it is utilized that these signals must present substantially the same pattern as the emitted signals. In this manner the picking up of even weak signals has been facilitated, whether these signals are weak or not compared to strong interference signals.</p> |
