| 摘要 |
During cloud height measurement according to the so- called "gating" method, the output signal of the receiver 6 is integrated during time slots which follow each other at the transmitting frequency but are offset in time with respect to the emission of light pulses 3. The time offset of the time slots is changed in steps according to a respective period. The signals, integrated in the individual time intervals are converted - by means of an analog/digital converter 11 - into digital signal values which are stored by a microprocessor 14 in a data memory 13 in the order of the height given by the time offset of the time slots. The microprocessor 14 forms a smooth function F2 of the signal values as a function of the height H. It differentiates the smooth function F2 with respect to the height H and determines the maximum and minimum values F3max.1, F3min.1 of the differentiated function F3 which are higher and lower, respectively, than a predetermined threshold value C1, C2. The microprocessor 14 subsequently selects the respective maximum value F3max which is followed by a minimum value F3min with increasing height H. The heights corresponding to the selected maximum values F3max are indicated as cloud heights if the signal values F1 associated with them exceed a threshold value C5 + F6. Thanks to this, clouds are reliably detected and wrong indications due to precipitation are avoided.
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