HCT Blood Glucose Meter  Reference Design

Paired with a sophisticated assessment platform, this solution integrates advanced analog front-end circuits, seamless data processing, and robust calibration capabilities. 

The HCT (Hematocrit) blood glucose meter is a precision device that employs an electrochemical method to measure DC current, AC impedance, and phase angle produced during the reaction between blood and a reactive enzyme. These measurements are utilized to calculate the exact blood glucose concentration. The meter functions in tandem with an assessment platform (AP), which facilitates calibration and testing. The AP directly communicates with the microcontroller unit (MCU) to initiate calibration and perform various measurement models. Once testing is completed, the MCU uploads the measured data to the AP, which processes the data to compute impedance and phase angle values for display. The results can also be exported into Excel for further analysis. The system delivers high accuracy, with a phase angle measurement error of ±0.3° and impedance measurement error of ±1%.

The design WAS-199CEN by Holtek integrates advanced features for robust and efficient operation. An Analog Front-End (AFE) circuit ensures accurate and stable measurements with minimal external components. The AFE includes a highly accurate voltage source with low-temperature drift, a DAC (Digital-to-Analog Converter), and operational amplifiers. This integration allows precise DC current measurement with only a few resistors and capacitors. Furthermore, the HCT AFE circuit supports multi-frequency, high-accuracy AC impedance and phase angle measurements without requiring external components. The hematocrit level is derived from these measurements, adding another layer of functionality.

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The solution comprises two main components: the HCT blood glucose meter development board with test strips and the BH67F2485 AC Impedance & Electrochemical Measurement Assessment Platform (AP). The development board performs continuous sampling and calculates DC current, AC impedance, and phase angle using electrochemical principles. These values are then adjusted using HCT compensation to determine the blood glucose concentration. The results are transmitted via a UART communication interface, ensuring seamless data exchange. Key specifications of the development board include a BH67F2485 MCU (80LQFP package), operating voltage range of 2.2V to 5.5V, impedance measurement range of 5kΩ–40kΩ (adjustable for specific requirements), and measurement accuracy of ±0.3° for phase angle and ±1% for impedance. The UART interface operates at 38400 baud rate with 8 data bits, no parity, and 1 stop bit.

The assessment platform (AP) complements the development board by commanding the MCU to adjust internal reference voltages and the 12-bit DAC output voltage. This platform ensures precise calibration and testing, enabling reliable operation and seamless integration with the development board for a comprehensive measurement solution.

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Holtek tests it, including system block diagrams, schematics, and PCB design files. This ensures users have access to all necessary resources for implementing, evaluating, and customising the solution. It features a robust power system based on high-performance components, ensuring reliability and efficiency.

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