腎結石形成風險評估之可攜式多參數尿液測試平台開發

Development of A Portable Multi-Sensor Urine Test Platform for Kidney Stone Formation Risk Assessment

盧思博(Roozbeh Falah Ramezani)

指導教授 ： 鍾文耀

中原大學/電機資訊學院/電子工程研究所/博士(2020年)

https://doi.org/10.6840/cycu202100959

摘要

這項工作介紹了基於物聯網 (IoT) 的多傳感器系統的開發，用於分析尿液質量。該系統設計用於測量尿樣中的四個參數：pH、離子鈣 (Ca2+) 濃度、尿酸水平和總溶解固體。離子敏感場效應晶體管 (ISFET) 形成 pH 傳感器，擴展柵極場效應晶體管 (EGFET) 形成 Ca2+ 濃度傳感器。浮橋恆壓恆流 (CVCC) 源形成電位讀出電路。電位計讀出電路用於通過在傳感器之間切換來測量 pH 值和鈣離子濃度。該系統設計用於 pH 2.0 至 10.0 的傳感範圍，分辨率為 0.1，整體精度優於 10%，鈣離子濃度範圍為 pCa 1.0 至 pCa 4.0，分辨率為 pCa 0.1，精度優於 10%。尿酸傳感器由電化學電池構成。使用了能夠與兩電極和三電極傳感器一起工作的寬範圍電流讀出電路。尿酸測量範圍為 20 ppm 至 500 ppm，分辨率為 1 ppm，精度優於 10%。電導率是用於測量尿液中總溶解電解質的指標。鍍金四電極電導率傳感器用於測量電導率。該系統還具有連接到兩電極電導率傳感器的靈活性。讀出電路包括一個三階模擬濾波器，它將來自數位後端的準方波信號轉換為正弦電壓。運算放大器 (op-amp) 配置為電壓電流轉換器，由模擬濾波器輸出的正弦電壓饋送。然後電流通過電導率傳感器的外電極並通過分流電阻返回電源。分流電阻器上的電壓使用高增益儀表放大器 (IA) 進行放大，然後通過有源低通濾波器。然後將信號饋送到數字後端電路的類比數位轉換器 (ADC)。類似的電路用於傳感器電壓電極和 ADC 之間。阻抗由電壓均方根 (RMS) 除以電流 RMS 值計算得出。在 1.5 kHz 和 3.3 kHz 之間的多個頻率範圍內，通過測量電壓和電流來重複阻抗計算。多頻率阻抗的回歸線被擴展到與y軸的截距。 Y 截點是零頻率下的阻抗，即電阻。將計算出的電阻值取反給出電導。電導率計算為電導乘以電池常數的結果。電導率測量範圍為 1.0 mS/cm 至 40.0 mS/cm，分辨率為 0.1 mS/cm，精度優於 10%。帶有嵌入式 12 位 ADC 的 ARM® cortex-M0+ 微控制器用作數字後端。數字後端用於控制所有測量的過程和時間，為電導率和尿酸讀數電路提供脈寬調製 (PWM) 信號，測量讀數電路的輸出電壓並執行所需的計算和校準，臨時存儲測量數據並與本地服務器通信以傳輸必要的信息。單板計算機用作提供互聯網連接的本地服務器，將測量結果存儲在本地數據庫中，在本地數據庫和雲之間同步數據並形成圖形用戶界面（GUI）。驗證過程是通過比較系統和商業儀器的測量結果來執行的。使用標準緩衝溶液和尿液重複該過程。商業緩衝溶液用於 pH 和 KCl，以分別評估 pH 和電導率測量系統的性能。用於評估 Ca2+ 和尿酸測量的緩衝溶液在我們的實驗室中製備。初步結果表明，該系統滿足了尿液質量分析所需的人體生理範圍內選擇的範圍、分辨率和準確度的要求。

關鍵字

尿液質量分析 ； 傳感器測量系統 ； 電流讀出電路 ； 電位讀出電路 ； 多頻電導率測量

並列摘要

This work presents the development of an Internet-of-Things (IoT)-base multi sensor system for analysis of urine quality. The system is designed for measurement of four parameters in urine sample: pH, concentrations of ionized calcium (Ca2+), uric acid level and total dissolved solids. An ion-sensitive field effect transistor (ISFET) forms the pH sensor and an extended gate field effect transistor (EGFET) forms the Ca2+ concentration sensor. A floating bridge constant voltage constant current (CVCC) source forms the potentiometric readout circuit. The potentiometric readout circuit is used for measuring the pH and calcium ion concentration by switching between the sensors. The system is designed for sensing range of pH between 2.0 and 10.0 with resolution of 0.1 and overall accuracy better than 10%, for calcium ion concentration the range is between pCa 1.0 and pCa 4.0 with pCa 0.1 resolution and accuracy better than 10%. Uric acid sensor is formed by an electrochemical cell. A wide-range amperometric readout circuit with ability to work with both two-electrode and three-electrode sensors is utilized. Measurement range for uric acid is between 20 ppm and 500 ppm with resolution of 1 ppm and accuracy better than 10%. Electro-conductivity is an index that used for measurement of total dissolved electrolytes in urine. A gold-coated four-electrode conductivity sensor is used for measurement of conductivity. The system also has the flexibility of connecting to two-electrode conductivity sensor. The readout circuit includes a 3rd order analog filter that converts the quasi-square signal from the digital back-end to sinusoidal voltage. An operational amplifier (op-amp) configured as voltage to current converter fed by the sinusoidal voltage from output of analog filter. The current then passes through the outer electrode of conductivity sensor and return back to the source through a shunt resistor. Voltage across the shunt resistor is amplified using high gain instrumentation amplifier (IA) and then passes through an active low-pass filter. Signal then fed to analog to digital converter (ADC) of digital back-end circuit. Similar circuit is used between sensor voltage electrodes and ADC. The impedance is calculated from voltage root mean square (RMS) divided by current RMS value. Impedance calculation is repeated from measurement of voltage and current in multiple frequencies range between 1.5 kHz and 3.3 kHz. The regression line of impedance in multiple frequencies is extended to intercept with y-axis. The Y-intercept point is the impedance at zero frequency which is the resistance. Inverting the calculated resistance value gave the conductance. Conductivity is calculated as result of multiplying conductance by cell constant. Measurement range for conductivity is between 1.0 mS/cm and 40.0 mS/cm with resolution of 0.1 mS/cm and accuracy better than 10%. An ARM® cortex-M0+ micro-controller with embedded 12-bit ADC is used as digital back-end. Digital back-end is used to control the process and the timing for all measurements, providing pulse-width-modulation (PWM) signals for conductivity and uric acid readout circuits, measuring the output voltage of readout circuits and perform the required calculation and calibrations, temporary storage of measurements data and communication with the local server to transfer necessary information. A single board computer is used as local server providing internet connectivity, storing the measurement results in local database, synchronizing the data between local database and cloud and forming the graphic user interface (GUI). Validation process is performed by comparison of measurement result from the system and commercial instruments. The process is repeated using both standard buffer solution and urine. The commercial buffer solutions are used for pH and KCl to evaluate performance of pH and conductivity measurement systems respectively. The buffer solution for evaluation of Ca2+ and uric acid measurement, are prepared in our laboratory. Preliminary results indicated that system satisfies the requirement for the range, resolution and accuracy as selected within the human physiological range needed for urine quality analysis.

並列關鍵字

Urine Quality Analysis ； -Sensor Measurement System ； Amperometric Readout Circuit ； Potentiometric Readout Circuit ； Multi-Frequency Conductivity Measurement

參考文獻

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