Abstract: Apparatus that detects the presence and condition of precipitation on the surface of a pathway. The apparatus has a block of electrically insulative material adapted to be embedded in the pathway with a top surface exposed to precipitation. A sensor is embedded in the block for sensing a physical property of the precipitation to produce a sensor output which is also influenced by a depth of the precipitation. Part of the top surface of the block has a well that is generally curved in outline above the sensor for gathering precipitation for the sensor. Advantageously, the influence of precipitation depth on the sensor is diminished. Other apparatus and methods are also disclosed.

Abstract: 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.