US 4,043,756 AGranted

Calibration in an automatic chemical testing apparatus

AssigneeHycel, Inc.

InventorDavid E. Sommervold

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Abstract

In an automatic chemical testing apparatus calibration values obtained from readout signals of analysis means must be stored for use in prior art calculating means for processing of subsequent readout signals of samples containing unknown quantities of substances in a medium. Improved means are provided for selecting the calibration values, namely a blank value and a reference value. A plurality of pairs of blank and reference samples are processed. The blank samples have known zero or baseline levels or concentrations of substances, and the reference samples have known concentration levels of each substance. These known values are stored for comparison to processed values obtained by processing the readout signals obtained in response to analysis of the blank and reference samples. The validity of each such readout signal as a calibration value is determined by the successfulness of the comparison. The most current successful blank and reference signals are selected as the calibration values. For verifying validity, the selected calibration values are utilized for processing signals obtained from a calibration control sample for which known substance concentration values are stored. A blank, reference and calibration control sample are processed as above at a later time for updating the calibration values during continued operation of the apparatus.

Claims22

Dependent claims

In an automatic chemical testing apparatus comprising readout means for producing readout signals indicative of optical density of samples wherein the wavelength at which optical density of a sample is measured is selected in correspondence with a particular chemistry being performed and the optical density at that wavelength is a function of the concentration of a particular substance therein for the particular chemistry, processing means for calculating a value of concentration units corresponding to the optical density indicated by the readout signal, wherein said processing means utilizes a predetermined curve function and wherein the predetermined curve function must be calibrated by the measurement of a blank sample and a reference sample each having a known concentration level of substances therein to provide calibration values indicative of a baseline and of a reference level for values of readout signals, and means for providing readout signals for a plurality of substantially identical blank samples and for a pluralty of substantially identical reference samples, the improvement of means for providing calibration values to said processing means comprising:

means for storing a first blank readout signal having a first blank value, means for storing a second blank readout signal having a second blank value, means supplying said second blank value to said processing means for obtaining a first blank concentration value based on the use of said second blank value as a calibration value, comparison means for measuring blank error between the first blank concentration value to a known stored blank concentration value for said blank sample, means responsive to said comparison means for supplying said second blank value to said processing means if the blank error is below a preselected level for providing said second blank value as a calibration value for processing of unknown samples.

In an automatic chemical testing apparatus comprising readout means for producing in each of a plurality of channels a readout signal indicative of optical density of an aliquot of a sample wherein the wavelength at which optical density of a sample aliquot is measured is selected in correspondence with a particular chemistry being performed and the optical density at that wavelength is a function of the concentration of a particular substance therein for the particular chemistry, processing means for calculating a value of concentration units corresponding to the optical density indicated by each of the readout signals, wherein said processing means utilizes a predetermined curve function for each channel and wherein the predetermined curve function must be calibrated by the messurement of a blank sample and a reference sample each having a known concentration level of substances therein to provide calibration values indicative of a baseline and of a reference level for values of readout signals, and means for providing readout signals for a plurality of substantially identical blank samples and for a plurality of substantially identical reference samples, the improvement of means for providing calibration values for each channel to said processing means comprising:

means for storing a first blank readpout signal having a first blank value, means for storing a second blank readout signal having a second blank value, means supplying said second blank value to said processing means for obtaining a first blank concentration value based on the use of said second blank value as a calibration value, comparison means for measuring blank error between the first blank concentration value to a known stored blank concentration value for said blank sample, means for storing said second blank value, means for providing a third blank value to said processing means for obtaining a second blank concentration value, means for obtaining a second blank concentration value, said comparison means further being connected for measuring blank error between said second blank concentration value, and means for providing a successful blank value to said processing means, as a calibration value, where a successful value is one the use of which results in a blank error below a preselected level.

In an automatic chemical testing method comprising in each of a plurality of channels a readout signal indicative of optical density of an aliquot of a sample wherein the wavelength at which optical density of a sample aliquot is measured is selected in correspondence with a particular chemistry being performed and the optical density at that wavelength is a function of the concentration of a particular substance therein for the particular chemistry, calculating in processing means a value of concentration units corresponding to the optical density indicated by each of the readout signals, wherein said processing means utilizes a predetermined curve function for each channel and wherein the predetermined curve function must be calibrated by the measurement of a blank sample and a reference sample each having a known concentration level of substance therein to provide calibration values indicative of a baseline and of a reference level for values of readout signals, and providing readout signals for a plurality of substantially identical blank samples and for a plurality of substantially identical reference samples, the improvement of a method for providing calibration values for each channel to said processing means comprising:

obtaining a blank readout signal for each blank sample having a blank value, supplying each said blank value to said processing means for obtaining a respective blank concentration value based on the use of the said blank value as a calibration value, comparing selected ones of said blank concentration values for measuring blank error between blank concentration values, comparing at least one of said blank concentration values to a known stored blank concentration value, and supplying a successful blank value to said processing means as a calibration value, where a successful value is one the use of which results in a blank error below a preselected level.

Dependencies are inferred from the claim text.