| 摘要 |
An apparatus for detecting the presence of ice or smooth packed snow on a road surface has a source of electromagnetic radiation, for example, a light emitting diode. This is mounted to illuminate an area of the road surface. It is driven by a modulating circuit at a known frequency. A detector is mounted adjacent the light source to receive radiation reflected back from the road surface, to generate a detector signal. This signal is demodulated by a demodulator to generate an intermediate signal. This is preferably compared with a fixed value, to determine whether the reflectivity of the road surface exceeds a set value, indicative of the presence of ice.
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