This invention relates to clinical analyzers. More particularly, a microprocessor-controlled spectrophotometric analyzing system is provided which incorporates unique calibration procedures to provide for highly accurate and dependable readings in a system which is relatively simple. The accurate calibration would be expected to be present only in systems much more expensive and much more complicated, and particularly those utilizing dual beam spectrophotometry.
It is known to analyze liquid-filled cuvettes spectrophotometrically to carry out clinical analyses. Many systems are on the market, and many are extremely complex in the handling of the cuvettes during testing. The present invention utilizes a shuttle which carries a number of cuvettes and which is moved by a stepper motor back and forth in a plurality of cycles past a single beam spectrophotometer. A microcomputer is utilized for all process control, namely, shuttle movement, filter wheel movement, calibration procedures, and control of all other process parameters.
In the past, single beam spectrophotometers have been subject to calibration difficulties due to circuit drift. Calibration problems are overcome in the present invention by utilizing unique calibration procedures so that calibration is always tightly controlled. In particular, energization of the lamp in the spectrophotometer is controlled, and lamp output is monitored to achieve optimum signal output and correct calibration. Additionally, the various filters employed in the spectrophotometer are frequently interrogated, and amplifier gain is adjusted for each filter to achieve optimum signal output. The gain for each filter is stored in the microprocessor and thereafter used for a test.
Additionally, a water-filled cuvette reference reading is taken whenever convenient, and is used in conjunction with air-only readings taken by the system often and at convenient times to provide for higly controlled, accurate, and frequent calibration of the circuitry.
The invention thus is broadly involved with process control, and specifically with process control in a clinical analyzer.
The invention will be more completely understood by reference to the following detailed description of a representative, but presently preferred embodiment thereof.