Abstract: A microprocessor controlled high precision electronic digital thermometer which is capable of producing highly accurate temperature readings while using relatively inexpensive components. The digital thermometer of the invention uses a thermistor probe to obtain highly accurate temperature measurements which may be obtained over an extended temperature range. The digital thermometer of the invention is constructed in a manner such that by using relatively inexpensive stable resistors in a bridge, highly accurate temperature readings may be obtained by rapid calibration and recalibration of the bridge in order to obviate the need for expensive precision resistors in the bridge circuit itself.

Abstract: A thermistor-type liquid temperature probe which includes a thermistor of low thermal capacity, and thermistor leads of low thermal conductivity. The probe also has low heat dissipation, and exhibits a high output signal level when connected to a measuring circuit. The thermistor itself is electrically isolated from the liquid whose temperature is being measured so that shunt leakage currentg across the thermistor is minimal.

Abstract: A digital temperature indicating system which enables a relatively inexpensive thermistor sensor to be used to obtain highly accurate temperature measurements over a number of relatively narrow temperature ranges, and to obtain acceptable temperature accuracy over an extended temperature range. The thermistor controls a bridge. The bridge produces an analog signal when the thermistor causes the bridge to become unbalanced from a null point as the thermistor senses different temperatures. The analog signal from the bridge is converted into digital signals which address memory locations in a programmable read-only memory (PROM) for both scaling and linearizing purposes. The resulting output signals from the PROM are used to control a display unit which displays the temperature readings.

Abstract: The temperature of a liquid bath in the tank of a clinical analyzer is precisely regulated to a known reaction temperature, for example, 37.0 degrees C., notwithstanding the transport of cuvettes through the tank by a conveyor for photometric analysis, by providing an electric heater assembly externally of the tank in a circulation loop through which the both liquid is circulated from a tank liquid outlet to a tank liquid inlet. The temperature of the liquid is measured by a first temperature sensor located downstream of the heater assembly but upstream of the tank inlet and a second temperature sensor located in the tank remote from the tank inlet. The deviation of the measured liquid inlet temperature from a preset liquid inlet temperature and the deviation of the measured tank temperature from the desired constant tank temperature are used to obtain a heating element drive signal for controlling the energization of the heater assembly to maintain the bath temperature constant.

Abstract: A microprocessor controlled data analyzing system is provided for use with a clinical spectrophotometer, such as the Abbott Bichromatic Analyzer (ABA-100), which is used for testing samples of serum derived from patients' blood. The data analyzing system of the invention serves to analyze the outputs from the spectrophotometer, and to transform the outputs into reportable units. The data analyzing system is capable of providing the operator with full instructions as to any particular test and to control the spectrophotometer to perform such a test.

Abstract: A photometric system is provided for use as a spectrophotometer system; or for use as a calibration system for accurately calibrating optical attenuators, such as neutral glass filters, interference-type filters, comb filters, screen filters, and the like. The photometric system of the invention includes a time-division optical attenuator which causes the precise fraction of a light beam to be passed through the system. The time-division optical attenuator is adjustable, so that when an optical attenuator to be calibrated, or a sample to be tested, is introduced into the optical path of the system, the light incident thereon can be changed precisely by any ratio of integers which returns the light output of the system to nearly its original reference level.

Abstract: A calibration system is provided for spectrophotometers of the type in which two or more wave lengths of light are caused to be transmitted through a sample cell. The calibration system may be used to calibrate spectrophotometers in which the beams are sequentially transmitted through the sample. In the practice of the invention, the sample is replaced with a number of accurately known optical attenuators which are introduced into the system in synchronism with the two light beams. The system provides calibration for both the scaling and linearization of the spectrophotometer, or conversely provides for the generation of tables and graphs which permit the operator to correct the photometer reading into an accurate representation.

Abstract: A sample cell is provided for spectrophotometers which is constructed to prevent stray light from being carried to the detector through the wall of the cell. This is achieved by configuring the cell wall in a manner so that it cannot function as a light pipe for the stray light, or by providing light attenuating means in the cell wall, or by providing an appropriate masking means in the wall.