ANALYSIS AND DESIGN OF A NOVEL CAPACITIVE SENSOR AND SIGNAL CONDITIONING CIRCUIT
|關鍵字:||信號調節電路;電容式感測器;積體電路;signal conditioning circuit;capacitive sensor;integrated circuit|
其次，本論文最新地提出一積體化之信號調節器，其為互補式金氧半導體之電容頻率轉換器且具有數位補償器。此轉換器是依據切換電容之技術，此技術已被展示為最合適實現在互補式金氧半導體的積體電路上，並且最合適地運用在變化的感測電容上。由於此轉換器之輸出訊號為脈波串，因此很容易地將其輸出借由如交換封包網路、無線電、光纖、紅外線、超音波等等傳輸媒介傳送。且經由數位補償器，此轉換器能夠具有寬範圍的動態頻率輸出之線性電容頻率轉換特性並且其準確性被大大地改善及提昇至+-5.14%。此偵測之電容變化範圍為4至24 pF，而其輸出頻率範圍為0.5至500 kHz。在電源3.2伏特之0.35微米之互補式金氧半導體之製程下，此設計於感測界面應用的轉換器，其所有的功能與成果被成功地檢測證實在HSPICE的模擬中。此實現的晶片面積為940x1080微米平方且其功率消耗為6.4毫瓦特。量測的結果已成功地驗證此積體化轉換器之動作效能。此轉換器不僅合適於電容量測系統，如壓力量測、流量計、濕度感測、位移感測器，也合適於運用需求在寬範圍的動態頻率輸出，如加速度計等等。此積體化信號調節器之研究，將可對於感測界面領域有所助益。|
In this thesis, firstly, a semi-cylindrical capacitive sensor with interface circuit using for flow rate measurement is newly proposed. The numerical analysis method to calculate the capacitance of the semi-cylindrical capacitive sensor is analyzed and discussed. The pF-range capacitive variation of the semi-cylindrical capacitive sensor can be detected and converted into voltage variation by the interface circuit. Besides, the interface circuit is compact to simplify the circuit complexity, and could be easily implemented for flow rate measurement. All the functions of the capacitive sensing method of the semi-cylindrical capacitive sensor using for flow rate measurement are proved successfully through HSPICE simulation. As analyzed, the bigger capacitance is expected to be increased the Silicone flow rate, and measured results are observed. Hence, by using the novel flow measuring techniques on the LCD panel coating machine, the mainframe can periodically monitor and immediately adjust the Silicone flow rate according to the calculated results. Measurement results have successfully confirmed the correct functions and performance of the semi-cylindrical capacitive sensor with interface circuit using for flow rate measurement on the LCD panel coating machine. The accuracy of the semi-cylindrical capacitive sensor with interface circuit is around ±6%. The proposed semi-cylindrical capacitive sensor has the great importance in the optoelectronics industry. Secondly, an integrated capacitive signal conditioning circuit is newly proposed. The proposed converter is based on the switched-capacitor (SC) techniques which had been shown to be the best suited for CMOS integrated circuits and operated with variable capacitance sensors. The output of the proposed converter is a pulse stream, it could be easily sent over a wide range of transmission media, such as PSN, radio, optical, IR, ultrasonic, and etc. With the novel digital compensation circuit, the proposed converter could have the rather linear capacitance-to-frequency transform characteristic over the wide dynamic output frequency range and the accuracy is greatly improved and promoted to ±5.14%. The output frequency range is from 0.5 to 500 kHz under the variable capacitance of the detected sensor ranges from 4 to 24 pF. Based upon 0.35 um 2P4M CMOS technology with 3.2 V power supply, all the functions and performance of the proposed converter are tested and proven through HSPICE simulations. Measurement results have successfully verified the correct functions and performance of the integrated capacitive signal conditioning circuit. The area of this implemented chip is 940x1080 um2 and the power consumption is 6.4 mW. The proposed converter is not only suitable for capacitive measurement systems, for example, applied in the interfaces of pressure measurement, flow meter, humidity sensing, displacement sensors, but also applications of demanding wide dynamic output frequency range, such as accelerometers, etc. Hence, the proposed capacitive signal conditioning circuit has the great importance in field of sensor interface.