| 摘要 |
Apparatus for determining the depth of precipitation accumulating on the surface of a pathway, such as an airport runway or the like, includes a sensor having electrical transducer means for emitting and sensing ultrasonic energy and having a body of material adapted to be embedded in the pathway with the top surface of the body being substantially flush therewith and exposed to the precipitation, the transducer means being physically coupled to the body. A circuit causes the transducer means to emit pulses of ultrasonic energy, which are reflected as first and second reflections from the top surface of the body and from the upper surface of an accumulation of precipitation on the top surface of the body and are respectively returned to the transducer which, in response to the reflected pulses, produces corresponding first and second electrical signals. An amplifier is connected to the transducer means for amplifying the first and second electrical signals corresponding to the first and second reflections, thereby to produce an amplifier output. Another circuit is connected to the amplifier for initiating a first timing signal upon the occurrence of the first electrical signal. A further circuit compares the amplifier output with a threshold level which has a magnitude that decreases with time, the operation of the comparing circuit being started upon an occurrence of the first timing signal, the comparing circuit initiating a second timing signal when the amplifier output reaches the threshold level. Still another circuit in the apparatus generates a third electrical signal representing the depth of the precipitation as a function of the time interval between occurrences of the first and second timing signals. Other circuits and methods for depth and related measurements are also described.
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