| Summary: | 碩士 === 國立中山大學 === 機械與機電工程學系研究所 === 106 === This study develops a solution sensing circuit device that combines the ITO chip for sensing pH, temperature and ion concentration that developed by our laboratory to complete the multi-parameter measurement of water quality and display the values instantly, and the mobile App is designed to remotely receive data via Bluetooth communication. This research uses the switching circuit design to solve the crosstalk between each sensor when doing multi-parameter measurement in the solution. In the sensing circuits design part, the pH measurement uses an EGFET, and the sensing chip is directly connected to the gate of the commercial transistor IC, and then the reference potential is given by the Ag/AgCl reference electrode to detect the pH of the solution. The change of the drain current caused by the concentration of the hydrogen ion is converted into the voltage through a TIA and an inverting amplifier, and it is convenient for the signal acquisition device to read. The temperature sensing measures the variance of resistance with Wheatstone bridge, and then reads the signal with the instrumentation amplifier. The ion concentration derived from the E.C., the sensing circuit architecture uses Wien bridge to produce a sinusoidal wave to measure the impedance in the solution, and the TIA converts the impedance change caused by different ion concentrations into a voltage output. The precision rectification circuit is used to convert the AC signal into a DC signal and filter it, and finally the voltage output is obtained. The sensing circuit combines the Arduino module to control the measurement and signal reception of the sensing circuit, and communicates with the Bluetooth module and the LCD for data output. In order to make the ITO sensing chip more convenient in packaging, the research improve into a new sensing chip module. The pH sensitivity measured by the circuit is 111.2 mV/pH, R2 = 0.9902, and the temperature measurement sensitivity is 60.2 mV/oC, R2 = 0.9994, the E.C. measurement is R2 = 0.9989, and the sensing circuit also has a response time of less than 10 ms. In the repetitive test, the C.V. of pH, temperature and E.C. of the chip was 0.097%, 0.997% and 0.230%, respectively. Finally, this study realize the prototype of the solution sensing device which can measure pH, temperature and ion concentration in the solution, successfully solve the crosstalk, and combine the data display and Bluetooth communication.
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