Method and apparatus for feedback stabilized photometric detection in fluids
A photometric detection method and apparatus employ a variable beam modulation device, such as a planar oscillating disk whose reflectance and transmittance with respect an incident beam of electromagnetic radiation vary with disk angular position, to form, from an incident beam of radiation, two amplitude modulated correlated component beams. Preferably the amplitudes of the component beams vary sinusoidally, 180/sup 0/ out of phase. In one illustrative embodiment, one of the component beams passes through a sample fluid, which absorbs a portion of the radiation at a wavelength characteristic of a selected component. The second component beam passes through a reference path and provides a reference signal relative to which changes in the sample fluid are measured. A feedback mechanism is provided to automatically adjust for variations which can occur while the apparatus is operating. The component beams are combined and are directed onto a detector which produces an output proportional to the intensity of the combined beam. By properly selecting the parameters of the system, the AC component of the combined signal, if any, provides a sensitive measure of the presence generally and if calibrated the relative density, of the selected sample fluid.
- Assignee:
- Panametrics Inc.
- Patent Number(s):
- US 4491730
- OSTI ID:
- 5844405
- Resource Relation:
- Patent File Date: Filed date 19 Oct 1981; Other Information: PAT-APPL-312936
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
FLUIDS
CHEMICAL ANALYSIS
DENSITY
PHOTOMETRY
PHOTODETECTORS
RADIATION DETECTORS
ABSORPTIVITY
ALTERNATING CURRENT
CALIBRATION
ENERGY ABSORPTION
FEEDBACK
INFRARED RADIATION
MODULATION
REFLECTIVITY
SENSITIVITY
VISIBLE RADIATION
ABSORPTION
CURRENTS
ELECTRIC CURRENTS
ELECTROMAGNETIC RADIATION
MEASURING INSTRUMENTS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
SURFACE PROPERTIES
440300* - Miscellaneous Instruments- (-1989)