System for detecting wet and icy surface conditions

• US 3,882,381 A
• Filed: 11/05/1973
• Issued: 05/06/1975
• Est. Priority Date: 11/05/1973
• Status: Expired due to Term

• Current Assignee: Robert O. Gregory
• Original Assignee: Robert O. Gregory
• Inventors: Gregory, Robert O.
• Primary Examiner(s): Krawczewicz, Stanley T.
• Application Number:
  US05/412,910
• Time in Patent Office: 547 Days
• Field of Search: 324/61R 340/234,235 317/246
• US Class Current: 324/667
• CPC Class Codes: G01N 27/226 Construction of measuring vessels; Electrodes therefor
• CPC Class Codes: G01W 1/00 Meteorology
• CPC Class Codes: G01W 1/14 Rainfall or precipitation gauges measuring volume in general G01F
• CPC Class Codes: G08B 19/02 Alarm responsive to formation or anticipated formation of ice

Abstract

A system for detecting wet and icy conditions on the surface of highways, airport runways and the like. A first capacitor is positioned on a surface the condition of which is being detected. This capacitor has first and second spaced-apart electrodes which are positioned substantially coplanar with the surface and exposed to atmospheric precipitation which affects the capacitor'"'"''"'"'s dielectric and capacitance. A second capacitor having first and second spaced-apart electrodes is positioned so as not to be exposed to atmospheric precipitation. Respective out-ofphase time-varying signals are applied to the first electrodes of said capacitors and the second electrodes are commonly connected. Means for indicating when the magnitude of a signal coupled to the commonly connected second electrodes reaches a predetermined magnitude provides an indication of the presence of any atmospheric precipitation on said surface.

Claims

1. A system for detecting wet and icy conditions on the surface of highways, airport runways and the like comprising:

a first capacitor adapted to be positioned on a surface the condition of which is to be detected, said capacitor having first and second spaced-apart electrodes adapted to be positioned substantially coplanar with said surface and exposed to atmospheric precipitation thereby to affect the dielectric and capacitance thereof;

a second comparator comprising first and second electrodes spaced from and substantially identical to and in registration with the aforesaid electrodes and adapted to be positioned so as not to be exposed to atmospheric precipitation;

means for concurrently applying respective out-of-phase timevarying signals to the first electrodes of said capacitors, said second electrodes being commonly connected; and

means for indicating when the magnitude of a signal coupled to the commonly connected second electrodes reaches a predetermined magnitude thereby to provide an indication of the presence of any atmospheric precipitation on said surface.

2. A system as set forth in claim 1 wherein the electrodes of said capacitors are covered by layers of electrical insulation.

3. A system as set forth in claim 2 wherein the electrodes of said second capacitor are covered by a layer of electrical insulation thicker than that of the layer covering the electrodes of said first capacitor.

4. A system as set foth in claim 2 wherein the electrodes of said first and those of said second capcitors are respectively interdigitated.

5. A system as set forth in claim 4 wherein the electrodes of said first capacitor are positioned on one surface of an insulative substrate and the electrodes of said second capacitor are positioned on the opposite surface of the substrate.

6. A system as set forth in claim 1 wherein said respective signals are substantially identical and 180* out-of-phase.

7. A system as set forth in claim 6 further comprising means for balancing the signals coupled to said second electrodes so that in the absence of any precipitation substantially no resultant signal is present at the second electrodes.

8. A system as set forth in claim 7 wherein the balancing means includes means for adjusting the magnitude of the signal applied to the first electrode of one of the capacitors.

9. A system as set forth in claim 1 wherein said respective time-varying signals are composites of a substantially constant amplitude lower frequency signal component and a substantially constant amplitude higher frequency signal component, and wherein said system further comprises a filter for separating the lower frequency signal component and the higher frequency signal component of any signal coupled to the commonly connected second electrodes.

10. A system as set forth in claim 9 in which the indicating means includes means responsive to the magnitude of any signal coupled to said second electrodes failing to reach said predetermined magnitude thereby to provide an indication of a clear surface condition.

11. A system as set forth in claim 10 in which the indicating means includes means responsive to the magnitudes of the responsive coupled signal components reaching said predetermined magnitude thereby to indicate a wet surface condition.

12. A system as set forth in claim 11 in which the indicating means includes means responsive to a change in the ratio of the magnitude of the coupled higher frequency signal component to the magnitude of the coupled lower frequency signal component thereby to indicate an icy surface condition.

13. A system as set forth in claim 9 wherein said respective time-varying signals applied to the first electrodes of said capacitors are substantially identical and 180* out-of-phase.

14. A system as set forth in claim 13 further comprising means for adjusting the magnitude of the signal applied to the first electRodes of one of the capacitors so that in the absence of any precipitation substantially no resultant signal is present on the second electrodes, and in which the indicating means includes means responsive to the substantial absence of any resultant signal being present at the commonly connected electrodes thereby to provide an indication of a clear surface condition.

15. A system as set forth in claim 14, which further includes means for adjusting the amplitudes of the lower frequency signal component and the higher frequency signal component to be equal.

16. A system as set forth in claim 15 in which the indicating means includes means responsive to higher and lower frequency signal components of substantially equal amplitudes in excess of said predetermined magnitude being coupled to the commonly connected electrodes thereby to indicate a wet surface condition.

17. A system as set forth in claim 16 in which the indicating means includes means responsive to a change in the ratio of magnitudes of said coupled higher and lower frequency signal components thereby to indicate an icy surface condition.

18. A systen as set forth in claim 9 wherein said lower frequency is in the order of 1000 Hz and said higher frequency is in the order of 200 KHz.