Apparatus for determining the average water film thickness of road surfaces
First Claim
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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Accused Products
Abstract
A system for determining the average water film thickness on surfaces, and in particular roadways, with the reflection of microwaves on the surface of the film of water being measured. To be able to easily measure water film thicknesses of several millimeters without contact and with great accuracy, the system includes at least two partial systems which each comprise a signal source and a receiver. The individual partial systems operate at different frequencies which are selected such that the maximum accuracy measuring regions associated with the respective frequencies are contiguous and cover the predetermined water film thickness range to be determined. The partial systems are connected with a sampling and control device which activates at least that partial system which exhibits maximum measuring accuracy for the respective water film thickness being measured and utilizes only the output signal from the receiver of that partial system for the measurement.
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Citations
14 Claims
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- the improvement comprising;
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10. A method for determining the average thickness d of a water film on a surface, where 0 ≦
- d ≦
10 mm, by measuring the reflection of microwaves on the surface of a film of water, said method including transmitting microwave signals at a given operating frequency from a signal source toward said surface, and receiving microwave signals at said given operating frequency reflected from said surface with a receiver which produces an output signal, whose magnitude corresponds to the thickness of a film of water on said surface, from the received signals;
the improvement comprising;providing first, second and third selectively activatable of said signal sources, and first, second and third of said receivers associated respectively with said first, second and third signal sources and producing respective first, second and third of said output signals, with said first signal source transmitting a first frequency between 24 and 24.25 GHz, said second signal source transmitting a second frequency between 2.4 and 2.5 GHz, and said third signal source transmitting a third frequency between 0.433 and 0.4348 GHz, when activated; and from said output signals of said receivers, determining and utilizing, as the film thickness measurement signal, only the said output signal from the one of said first, second and third receivers whose associated operating frequency exhibits the maximum measuring accuracy at the respective water film thickness currently being measured. - View Dependent Claims (11, 12, 13, 14)
- d ≦
Specification