Colorimetric fluid analyzer
AssigneeBeckman Instruments, Inc.
InventorsRobert J. Ehret, Donald E. Stephens, Douglas H. Durland, Thomas D. Sharples
Life of this patent
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Abstract
A light beam is passed through a cuvette, through which flows liquid to be analyzed optically for concentration of color reacted amino acids. The emergent beam is directed through a series of dichroic beam separators and pass band filters to produce three beams of substantially three different wavelengths. Photoelectric detectors produce electrical signals corresponding to each of the three wavelengths. Two of the signals are characteristic of the substance to be detected. The third is subtracted from the other two wavelength signals to produce a pair of output signals from which base line noise has been substantially eliminated.
Claims20
A colorimeter responsive to color properties of a fluid comprising:
- a cuvette;
- means for flowing a fluid through the cuvette and projecting a light beam through the cuvette and the fluid to be analyzed along a first path;
- detector means responsive to the energy of the light beam;
- converting means comprising logarithmic amplifier means connected to said detector means;
- a first dichroic beam separator interposed after said cuvette in said first path for deflecting light below a first selected wavelength in a second beam along a second path and transmitting light above said selected wavelength along said first path;
- a second dichroic beam separator interposed after said first beam separator in said first path for deflecting light below a second selected wavelength in a third beam along a third path and transmitting the remaining light above said second selected wavelength along said first path;
- the detector means comprising detectors interposed in each of said first, second and third paths responsive to the energy of the light beams therein for producing first, second, and third electrical output signals corresponding to the intensity of the energy of light in said first, second and third paths;
- and
- said converting means being connected to receive said signals from said first and third detectors and from said first and second detectors, said converting means comprising logarithmic operational amplifiers whereby the signals representing transmittance of light are converted into signals proportional to absorbance at the wavelengths in question to produce electrical output signals representative of the difference of the optical absorbances within said cuvette of light between said third beam and said first beam and of the optical absorbances within said cuvette of light between said second beam and said first beam.
A cuvette holder for use in the measurement of fluid properties comprising a cylinder having a coaxial bore, a substantially radial bore at one end of the axial bore and a second substantially radial bore at the opposite end of the axial bore whereby a cuvette extending longitudinally and having transverse openings at the ends may be mounted in the axial bore and have fluid connections brought through the radial bores in said cylinder, wherein the improvement comprises sealing means in each radial bore for forming fluid tight junctures with the transverse openings of the cuvette, said sealing means each including a packing nut having an inner end;
- a ferrule fitting against said inner end of said packing nut and having a bore countersunk at the inner end of the ferrule;
- a tube extending through said packing nut and said ferrule with a flared inner end;
- a connector fitting with a collar intermediate the ends of the connector fitting;
- said connector fitting having a conical outer end and said radial bore in the cuvette holder being counterbored to receive said connector fitting, whereby said packing nut is adapted to clamp said flared end of said tube between said countersunk ferrule bore and said connector fitting outer end, and said connector includes an O-ring at its end opposite said conical end, said O-ring abutting said cuvette to form a fluid tight junction with a transverse opening of said cuvette.
Apparatus for measuring optical properties of a fluid having an optical line of sight from a light source to a light responsive element comprising:
- a cuvette for receiving fluid the properties of which are to be measured, said cuvette including an elongated chamber extending along said optical line of sight;
- an optical head surrounding said line of sight and said cuvette;
- a fluid circuit for supplying fluid sample to said cuvette, said fluid circuit including a coil of tubing in thermal relation to said optical head, said cuvette and coil positioned in close proximity to each other so that the liquid in the cuvette and the optical head are brought into thermal equilibrium.
A colorimeter for analyzing the absorbance of a fluid flowing through a cuvette comprising:
- a cuvette;
- means for flowing a fluid through the cuvette and projecting a light beam through the cuvette and the fluid to be analyzed along a first path;
- a first dichroic beam separator interposed after said cuvette in said first path for transmitting a portion of the light in said first path along said first path and for deflecting the remainder of the light in said first path, said dichroic beam separator acting selectively to transmit or deflect light of a wavelength above or below a first selected wavelength, the deflected light being in a second beam along a second path;
- a second dichroic beam separator in one of said light beam paths, said second dichroic beam separator acting selectively for transmitting a portion of the light along the path in which it is located and deflecting the remaining light in a beam along a third path, the second dichroic separator acting selectively with respect to transmission and deflection of light according to whether light in the path in which the second dichroic separator is located is of a wavelength above or below a second selected wavelength;
- first, second and third detector means positioned respectively in each of said first, second and third light paths responsive to energy of said light beams;
- and
- converting means including logarithmic amplifier means connected to receive output signals from said first, second and third detectors representing transmittance of light through said cuvette and converting said signals into signals proportional to absorbance, said logarithmic amplifier means producing output signals representing the difference between the optical absorbances within said cuvette of light in the highest selective wavelength from the optical absorbances of light in the lower selected wavelengths.
Dependencies are inferred from the claim text.