COMB FILTER PRESSURE/TEMPERATURE SENSING SYSTEM

• Main Authors: ELVIN E. HERMAN, BART E. LIKES
• Format: Patent
• Language: English
• Published: 22.09.1989
• Edition: 4
• Subjects: ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVEREDIN A SINGLE OTHER SUBCLASS; MEASURING; MEASURING ANGLES; MEASURING AREAS; MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER,MECHANICAL EFFICIENCY, OR FLUID PRESSURE; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS; MEASURING LENGTH, THICKNESS OR SIMILAR LINEARDIMENSIONS; MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR; MEASURING QUANTITY OF HEAT; MEASURING TEMPERATURE; PHYSICS; TARIFF METERING APPARATUS; TESTING; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR

A sensing system having a wideband optical source for providing optical illumination having a bandwidth of at least 25 nanometers, and an optical fiber cable for transmitting the optical illumination to a remote location. A transducer responsive to the transmitted optical illumination amplitude modulates the transmitted optical illumination as a function of a monitored physical parameter (for example, pressure or temperature) to provide an amplitude modulated optical illumination having generally sinusoidally varying nulls across the spectrum thereof, the frequency of the nulls varying across the spectrum of the modulated optical illumination and being a function of the monitored physical parameter. The fiber optic cable (or another fiber optic cable, depending on the transducer implementation) transmits the modulated optical illumination to an optical spectral analyzer which provides a spectrally dispersed optical signal indicative of the spectral content and amplitudes of the modulated optical illumination. A clocked detector array responsive to the spectrally dispersed optical signal is clocked at a varying clock rate to remove the frequency variation of the periodic nulls across the optical spectrum, so as to provide an electrical signal having a substantially constant frequency of the nulls. Narrowband filtering circuitry filters the electrical signal of substantially constant frequency to provide a filtered signal, and output circuitry responsive to the filtered signal provides an output signal indicative to the substantially constant frequency of the periodic nulls.