Calibration in a blood analyzer
First Claim
1. In a spectrophotometric measuring system for analyzing the concentration of a substance in a sample as a function of optical density of the sample, calibration means comprising first and second photodetectors positioned for respectively receiving radiant energy of a source and radiant energy applied from the source through a sample;
- ratio means connected to said photodetectors for providing an output as a function of the ratio of the outputs of said first and second detectors;
a programmable voltage source;
summing amplifier means having outputs from said ratio circuit and from said programmable voltage source coupled thereto for summing the outputs thereof, measuring means for measuring an output indicative of the output of said summing amplifier;
a progammable gain amplifier coupled between said programmable voltage source and said measuring means;
control means connected to said measuring means, and providing outputs coupled to program said programmable voltage source and said programmable gain amplifier;
blank mode selection means for selection in correspondence with placing of a blank sample between said source and said second photodetector for connecting said control means for setting gain of said programmable gain amplifier at a preselected level and for providing a programming signal to said programmable voltage source;
said control means further comprising blank level means for providing a value indicative of a desired blank level;
means for comparing the output of said summing means to the output of said blank level means and for providing the programming signal to reduce the error between the value and the output of said summing means below a predetermined level, and means for holding and applying said programming signal to said programmable voltage source in an operate mode in which an unknown sample is placed between the source and said second photodetector.
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Abstract
In a blood analyzer, improved calibration is provided. First and second photodetectors sense energy supplied directly from a source and from the source through a sample respectively. A log ratio amplifier provides an analog output indicative to the log of the ratio of the outputs of the photodetectors to a control circuit. When a blank sample is measured, a programmable voltage source operates to set the analog output to a selected level. A reference sample having optical density corresponding to a preset value is next measured, and a variable gain amplifier is set by the control circuit to cause the analog signal to correspond to the preset value.
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Citations
10 Claims
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1. In a spectrophotometric measuring system for analyzing the concentration of a substance in a sample as a function of optical density of the sample, calibration means comprising first and second photodetectors positioned for respectively receiving radiant energy of a source and radiant energy applied from the source through a sample;
- ratio means connected to said photodetectors for providing an output as a function of the ratio of the outputs of said first and second detectors;
a programmable voltage source;
summing amplifier means having outputs from said ratio circuit and from said programmable voltage source coupled thereto for summing the outputs thereof, measuring means for measuring an output indicative of the output of said summing amplifier;
a progammable gain amplifier coupled between said programmable voltage source and said measuring means;
control means connected to said measuring means, and providing outputs coupled to program said programmable voltage source and said programmable gain amplifier;
blank mode selection means for selection in correspondence with placing of a blank sample between said source and said second photodetector for connecting said control means for setting gain of said programmable gain amplifier at a preselected level and for providing a programming signal to said programmable voltage source;
said control means further comprising blank level means for providing a value indicative of a desired blank level;
means for comparing the output of said summing means to the output of said blank level means and for providing the programming signal to reduce the error between the value and the output of said summing means below a predetermined level, and means for holding and applying said programming signal to said programmable voltage source in an operate mode in which an unknown sample is placed between the source and said second photodetector. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- ratio means connected to said photodetectors for providing an output as a function of the ratio of the outputs of said first and second detectors;
Specification