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Apparatus for determining the average water film thickness of road surfaces

  • US 5,105,157 A
  • Filed: 12/06/1990
  • Issued: 04/14/1992
  • Est. Priority Date: 12/09/1989
  • Status: Expired due to Fees
First Claim
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1. In a system for determining the average thickness of a water film on a surface by measuring the reflection of microwaves on the surface of a film of water, said system including at least one signal source means for transmitting microwave signals at a given operating frequency toward said surface and at least one receiver means for receiving microwave signals at said given operating frequency reflected from said surface and for producing an output signal whose magnitude corresponds to the thickness of a film of water on said surface;

  • the improvement comprising;

    at least first and second of said signal source means and first and second of said receiver means associated respectively with said first and second signal source means, with each of said signal source means operating at a different frequency and with the respective frequencies being selected such that the measuring regions of maximum measuring accuracy associated with the respective frequencies are contiguous and cover the given water film thickness range to be measured; and

    ,sampling and control means, responsive to the respective said output signals from said receiver means, for causing evaluation of only the said output signal from the one of said receiving means whose associated operating frequency exhibits the maximum measuring accuracy at the respective water film thickness being measured.

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