Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Analysis of complex waves
Patent
1987-05-08
1987-12-29
Tokar, Michael J.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Analysis of complex waves
324 78R, 331 25, G01R 2316
Patent
active
047163631
ABSTRACT:
Oxygen determination based on luminescence quenching of fluorescent dye is effected by using the frequency output of an offset-phase locked loop to calculate the time constant for the exponential decay of fluorescence. An offset phase angle between a periodic stimulus signal used to excite the dye and a response signal based on fluorescence detection is predetermined to optimize signal-to-noise ratio for a wide range of time constants. An offset-phase locked loop is used to vary the frequency of a periodic stimulus signal until the predetermined phase relationship is established. Where the stimulus and response signals are substantially sinusoidal, the offset phase angle is ideally about 49.3.degree., although substantially optimal performance is achieved using a more conveniently generated 45.degree.. The 45.degree. angle offset can also be used with a square-wave stimulus signal.
REFERENCES:
patent: 3939405 (1976-02-01), Mutziger
patent: 4109283 (1978-08-01), Rast
patent: 4670887 (1987-06-01), Heatherington
Carlsen, Jr. William F.
Dukes John N.
Pittaro Richard J.
Anderson Clifton L.
Frazzini John A.
Hewlett--Packard Company
Tokar Michael J.
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