Optical analytical instrument and method having improved calibration

Claim 2

An optical analytical instrument for quantitative measurements capable of producing amplitude readings based upon the effect of a fluid upon a selected fixed wavelength in a beam of optical radiation to determine a quantitative physical parameter of the fluid, said instrument comprising a source of suitable optical radiation, a detector means responsive to said selected fixed wavelength within a predetermined amplitude measurement range of the instrument, means defining a zone for said fluid, means defining an optical path from said radiation source through said fluid zone to said detector means, reading and control circuitry for taking from said detector means at least two amplitude readings of optical energy of said selected fixed wavelength that result from the influence of the fluid on said optical radiation without there having occurred substantial change to the fluid, means during one of said readings for including in said optical path a filter of known absorbance that absorbs a predetermined portion of the energy at said fixed wavelength, said portion representing a substantial fraction of said amplitude measurement range of the instrument so that the respective reading represents an amplitude calibration reading within said measurement range of the instrument, calibration-value-determining means operable while a sample of said fluid remains unchanged in said fluid zone, first to compare, effectively, said two amplitude readings at said selected fixed wavelength to remove said effect of said fluid from the value of said calibration reading, second, to compare, effectively the residual value of said calibration reading to a known value based on the known absorbance of said filter, and, third, on the basis of said second comparison, to determine an amplitude calibration value for said instrument based on amplitude values derived while said fluid sample remains unchanged in said fluid zone.

Claim 3

An optical analytical instrument capable of producing readings based upon the effect of a fluid upon a beam of optical energy to determine a physical parameter of the fluid, said instrument comprising a source of suitable optical radiation, a detector means, means defining a zone for said fluid, means defining an optical path from said radiation source through said fluid zone to said detector means, reading and control circuit for taking from said detector means at least two readings of optical energy that has been influenced by the fluid without there having occurred substantial change to the fluid, means during one of said readings for including in said optical path a filter of known absorbance so that the respective reading represents a calibration reading, calibration-value-determining means constructed first to compare, effectively, said two readings to remove said effect of said fluid from the value of said calibration reading, second, to compare, effectively the residual value of said calibration reading to a known value based on the known absorbance of said filter, and, third, on the basis of said second comparison, to make a calibration adjustment based on values derived while said fluid sample remained unchanged in said fluid zone, wherein said optical radiation source comprises two separately energizable radiation emitters, said optical path from said source having two branches, one defining a respective optical path from each radiation emitter, with both branches transmitting via a substantially common path through said sample, one of said emitters, denoted the "measure" emitter, energized by said control means during the taking of a normal measurement reading and the other emitter, denoted the "calibration" emitter, energized by said control means during the taking of a calibration reading, said filter of known absorbance being included in the optical path from said calibration emitter to said fluid zone.

Claim 4

An optical analytical instrument capable of producing readings based upon the effect of a fluid upon a beam of optical energy to determine a physical parameter of the fluid, said instrument comprising a source of suitable optical radiation, a detector means, means defining a zone for said fluid, means defining an optical path from said radiation source through said fluid zone to said detector means, reading and control circuit for taking from said detector means at least two readings of optical energy that has been influenced by the fluid without there having occurred substantial change to the fluid, means during one of said readings for including in said optical path a filter of known absorbance so that the respective reading represents a calibration reading, calibration-value-determining means constructed first to compare, effectively, said two readings to remove said effect of said fluid from the value of said calibration reading, second, to compare, effectively the residual value of said calibration reading to a known value based on the known absorbance of said filter, and, third, on the basis of said second comparison, to make a calibration adjustment based on values derived while said fluid sample remained unchanged in said fluid zone, wherein said optical radiation source comprises two separately energizable radiation emitters, said optical path from said source having two branches, one defining a respective optical path from each radiation emitter, with both branches transmitting via a substantially common path through said sample, one of said emitters, denoted the "measure" emitter, energized by said control means during the taking of a normal measurement reading and the other emitter, denoted the "calibration" emitter, energized by said control means during the taking of a calibration reading, said filter of known absorbance being included in the optical path from said calibration emitter to said fluid zone.

Claim 5

An optical analytical instrument capable of producing readings based upon the effect of a fluid upon a beam of optical energy to determine a physical parameter of the fluid, said instrument comprising a source of suitable optical radiation, a detector means, means defining a zone for said fluid, means defining an optical path from said radiation source through said fluid zone to said detector means, reading and control circuitry for taking from said detector means at least two readings of optical energy that has been influenced by the fluid without there having occurred substantial change to the fluid, means during one of said readings for including in said optical path a filter of known absorbance so that the respective reading represents a calibration reading, calibration-value-determining means constructed first to compare, effectively, said two readings to remove said effect of said fluid from the value of said calibration reading, second, to compare, effectively the residual vale of said calibration reading to a known value based on the known absorbance of said filter, and, third, on the basis of said second comparison, to make a calibration adjustment based on values derived while said fluid sample remained unchanged in said fluid zone, wherein said optical radiation source comprises two separately energizable radiation emitters, said optical path from said source having two branches, one defining a respective optical path from each radiation emitter, with both branches transmitting via a substantially common path through said sample, one of said emitters, denoted the "measure" emitter, energized by said control means during the taking of a normal measurement reading and the other emitter, denoted the "calibration" emitter, energized by said control means during the taking of a calibration reading, said filter of known absorbance being included in the optical path from said calibration emitter to said fluid zone, and wherein said instrument has no moving parts for accomplishing calibration, said control means constructed and arranged such that normal and calibration readings for use by said instrument in establishing said calibration adjustment are effected by selective energization of said emitters during operation.

Claim 6

An optical analytical instrument capable of producing readings based upon the effect of a fluid upon a beam of optical energy to determine a physical parameter of the fluid, said instrument comprising a source of suitable optical radiation, a detector means, means defining a zone for said fluid, means defining an optical path from said radiation source through said fluid zone to said detector means, reading and control circuitry for taking from said detector means at least two readings of optical energy that has been influenced by the fluid without there having occurred substantial change to the fluid, means during one of said readings for including in said optical path a filter of known absorbance so that the respective reading represents a calibration reading, calibration-value-determining means constructed first to compare, effectively, said two readings to remove said effect of said fluid from the value of said calibration reading, second, to compare, effectively the residual vale of said calibration reading to a known value based on the known absorbance of said filter, and, third, on the basis of said second comparison, to make a calibration adjustment based on values derived while said fluid sample remained unchanged in said fluid zone, wherein said optical radiation source comprises two separately energizable radiation emitters, said optical path from said source having two branches, one defining a respective optical path from each radiation emitter, with both branches transmitting via a substantially common path through said sample, one of said emitters, denoted the "measure" emitter, energized by said control means during the taking of a normal measurement reading and the other emitter, denoted the "calibration" emitter, energized by said control means during the taking of a calibration reading, said filter of known absorbance being included in the optical path from said calibration emitter to said fluid zone, and wherein said instrument has no moving parts for accomplishing calibration, said control means constructed and arranged such that normal and calibration readings for use by said instrument in establishing said calibration adjustment are effected by selective energization of said emitters during operation.

Claim 7

The optical analytical instrument of claim 1, 2 or 3 in the form of an in-line analytical instrument in which said means defining said fluid zone comprises a conduit for at least part of a process stream through which process fluid flows, said process stream having a characteristic maximum rate at which said parameter can change, and said reading and control means constructed, in relation to said process stream, to take said two readings within such a short time interval that there is insufficient passage of time to allow substantial change to occur in said parameter of said fluid in said process stream.

Claim 8

The optical analytical instrument of claim 1, 2 or 3 in the form of a titration chamber constructed to be filled by a liquid process stream and, after titration, flushed only by the process stream.

Claim 9

The optical analytical instrument of claim 1, 2 or 3 in the form of a titration chamber constructed to receive a known repeatatable small sample of process stream liquid and after titration said chamber is constructed to be flushed with a suitable liquid.

Claim 10

The optical analytical instrument of claim 5 in the form of a colorimeter.

Claim 11

The optical analytical instrument of claim 1, 2 or 3 in the form of a colorimeter, the portion of said optical path in said fluid zone being defined by a probe which includes a reflector whereby energy which enters said fluid zone is reflected to pass back through said fluid zone to said detector means.

Claim 12

The optical analytical instrument of claim 1, 2 or 3 in the form of an absorption spectrophotometer, said detector means comprising at least two detectors sensitized to respectively different wavelengths, one wavelength corresponding to a characteristic absorption of a component of interest in said fluid zone, the detected signal varying with the concentration of said component, and the other wavelength being a reference wave-length for which said component of interest has relatively low absorbance.

Claim 13

The optical analytical instrument of claim 1 or 2 wherein said detector means is positioned to receive scattered or fluorescent radiant energy from said sample.

Claim 14

The optical analytical instrument of claim 10 wherein said filter is positioned to filter said scattered or fluorescent radiant energy.

Claim 15

The optical analytical insturment of claim 10 wherein said detector is postioned to receive Raleigh scattering or fluorescence.

Claim 16

The optical analytical instrument of claim 1 in the form of a turbidimeter.

Claim 17

The optical analytical instrument of claim 13 further including an optical reference path bypassing said sample.

Claim 18

The optical analytical instrument of claim 1, 2 or 3 wherein said means defining said optical path from said radiation source to said fluid zone is comprised of optical fibers.

Claim 19

The optical analytical instrument of claim 1, 2 or 3 wherein said means to make a calibration adjustment is constructed to calibrate the instrument.

Claim 20

The optical analytical instrument of claim 16 wherein said means responsive to make said calibration adjustment comprises means to adjust the sensitivity of the instrument.

Claim 21

The optical analytical instrument of claim 16 wherein said means to make said calibration adjustment comprises means to adjust the zero reference of said instrument.

Claim 22

The optical analytical instrument of claim 1, 2 or 3 including means to provide said known value in the form of means to store a reading of the detector means taken with said filter of known absorbance in place and with said fluid zone empty.

Claim 23

The optical analytical instrument of claim 6 in the form of a colorimeter.

Claim 24

The optical analytical instrument of claim 1 wherein said substantial fraction is of the order of 30 percent.

Claim 25

The optical analytical instrument of claim 1 wherein said instrument has no moving parts for accomplishing calibration.

Claim 32

The method of claim 23, 24 or 25 wherein said fluid flows in a process stream further comprising taking two readings by said control means within such a short time interval that there is insufficient passage of time to allow substantial change to occur in said parameter of said fluid in said process stream.

Claim 33

The method of claim 23, 24 or 25 further including the steps of filling a titration chamber by a liquid process stream and, after titration, flushing said titration chamber only by the process stream.

Claim 34

The method of claim 23, 24 or 25 further including the steps of filling a titration chamber by a liquid process stream and, after titration, flushing said titration chamber by a suitable liquid.

Claim 35

The method of claim 27 wherein the calibration is performed for a colorimeter.

Claim 36

The method of claim 23, 24 or 25 wherein the calibration is performed for an absorption spectrophotometer.

Claim 37

The method of claim 23, 24 or 25 wherein the calibration is performed for an instrument responsive to Raleigh scattering or fluorescence.

Claim 38

The method of claim 23, 24 or 25 wherein the calibration is performed for a turbidimeter.

Claim 39

The method of claim 23, 24 or 25 wherein said step of making a calibration adjustment calibrates the instrument.

Claim 40

The method of claim 33 wherein said calibration adjusts the sensitivity of the instrument.

Claim 41

The method of claim 33 wherein said calibration adjusts the zero reference of the instrument.

Claim 42

The method of claim 23, 24 or 25 further including the step of storing a reading of the detector means taken with said filter of known absorbance in place and with said fluid zone empty.

Claim 43

The method of claim 23, 24 or 25 wherein said step of making a calibration adjustment includes updating a current filter absorbance value.

Claim 44

The method of claim 37 wherein said calibration adjustment step is periodically repeated and said current filter value is successively updated during these repetitions.

Claim 45

The method of claim 37 wherein past trends in said current absorbance value are taken into consideration in updating said current absorbance value.

Claim 46

The apparatus of claim 1 or the method of claim 23 wherein, respectively, the instrument is constructed or the method is conducted to measure concentration or the like, C, according substantially to the relationship ##EQU4## in which the values are substantially as defined in the foregoing specification.

Claim 47

The method of claim 28 wherein the calibration is performed for a colorimeter.

Claim 48

The method of claim 23 wherein said substantial fraction is of the order of 30 percent.

Claim 49

The method of claim 23 wherein said calibration adjustment is effected without moving any parts of said instrument.