Blood Glucose and Other Diagnostic Meters

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New innovations in diagnostic equipment are making it easier than ever to test quickly for a number of critical care assays in blood such as blood gases, glucose, electrolytes, coagulation, chemistries, hematology and cardiac markers (cTnl) . With the advent of new digital technologies, invasive blood analyzers have become portable and are used to measure the two major assays of metabolic disorders in blood system: glucose and cholesterol .


The two methods used for blood analyte measurement are the color reflectance method and the amperometric method (electrochemical sensor technology) .


The analog front-end of the reflectance method uses topical sensors (LED, photo transistors) and a transimpedance amplifier . Measurements made using the color reflectance method are based on reaction color intensity in the reaction layer of the test strip by reflectance photometry . The meter quantifies the color change and generates a numerical value that represents the concentration of cholesterol/glucose in blood.


Using the amperometric method, the biosensor (test strip) is connected directly to the transimpedance amplifier . Cholesterol/glucose present in the blood, while undergoing chemical reaction with the test strip, generates charge and is measured by the amperometric method . An ambient temperature measurement is also necessary for test strip characteristic compensation.


The measurement sequence is usually controlled by a microcontroller (MCU) .The MCU also processes the conversion results, storing the measurements in an EEPROM or Flash memory and controlling other functions such as the keypad, real-time clock, sound/speech compression and serial communication to a connected computer .
The audio output is provided by either a PWM circuit or from the DAC . Both can be used to generate beeping sounds to signal when measurement results are available . They also generate voice instructions from the speech-synthesizer software using ADPCM compression algorithms . Measurement results are stored with the measurement time and date in the EEPROM or Flash memory as a data log that can be uploaded to a computer via wireless interface .
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