Exponential decay time constant measurement using frequency of offset phase-locked loop: system and method
US4716363A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 8, 1987 |
| Grant date | Dec 29, 1987 |
| Priority date | — |
| Expiry date | May 8, 2007 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T436/209163
- WIPO fieldMeasurement
- WIPO sectorInstruments
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.