Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Distributive type parameters
Patent
1995-12-13
1997-11-11
Karlsen, Ernest F.
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Distributive type parameters
324633, 324637, 324648, 244134F, 340582, G01N 2200, G01K 2704
Patent
active
056868413
ABSTRACT:
An embodiment of the present invention is a roadway sensor for surface installation in a hole such that a thin ceramic contact sensor may be used to measure and cross-compare fundamental physical antenna parameters of the space immediately above a roadway or bridge surface. Measurements are combined by a microprocessor to discriminate between dry pavement, water (rain), snow and ice above the sensor head. Ambient surface temperature, water depth and ice/slush conditions are determined to estimate any hydroplaning hazard and ice/antifreeze/water mixtures. The sensor comprises an antenna that exhibits a resonant frequency and an input admittance including a real term; a Maxwell bridge coupled to the antenna for detecting the resonant frequency, input admittance and real term; and a frequency sweeping oscillator for driving the antenna at a plurality of frequencies proximate in frequency to the resonant frequency. A phase sensitive detector determines an attenuation rate and phase and thereby is able to extract a conductivity (.sigma.) and a dielectric (.epsilon.) measurement. The microprocessor relates the conductivity and dielectric measurements to yield, for example, a pair of estimates for ice and water content and layer thickness.
REFERENCES:
patent: 5072172 (1991-12-01), Stolarczyk
patent: 5440238 (1995-08-01), Martens et al.
patent: 5474261 (1995-12-01), Stolarczyk et al.
patent: 5497098 (1996-03-01), Heil et al.
R.N. Grubb, P.L. Orswell, J.H. Taylor, "Borehole measurements of conductivity and dielectric constant in the 300 KHz to 25 MHz frequency range," Radio Science, vol. 11, No. 4, pp. 275-283, Apr. 1976 (Published by the American Geophysical Union, Washington, DC).
Stolarczyk Gerald Lee
Stolarczyk Larry G.
Do Diep
Karlsen Ernest F.
Schatzel Thomas E.
Stolar, Inc.
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