| 摘要 |
Snow depth gauge comprising: an elongate support 1 for use in an upright orientation; a multiplicity of emitters 2, possibly LEDs emitting light, and a multiplicity of detectors 3, possibly sensitive to at least two signal levels, mounted spatially apart along the support. The emitters 2 and the detectors 3 are electrically connected to a processor which can send signals to the emitters 2 and receive signals from the detectors 3. According to a first aspect, there are at least two sets of such emitters 2 or at least two sets of such detectors 3. The sets are directed in different respective directions, maybe outward. The emitters 2 may be triggered in succession from upward from bottom to top. An ambient signal may be stored/compared and dividers 9, 10 between emitters 2 and detectors 3. According to a second aspect, different emitters 2 and/or detectors 3 can transmit/receive radiation at a plurality of different respective ranges of frequencies. Radiation from outside selected ranges is either not used or is only used at a reduced level compared to the radiation used within that range. The ranges may be narrow enough to represent individual frequencies such as 0.6, 1.1 or 1.65 microns. |
