| Summary: | 碩士 === 中原大學 === 電子工程研究所 === 98 === In recent years, the environment and quality of life has become an important issue. Environmental and livelihood related water quality monitoring has become a topic of interest for research. The target is to be able to integrate a sensor that detects a variety of ion with wireless transmission to form a long term monitoring system.
This study prepared a sodium sensor based on ion-sensitive field-effect transistor combined with a commercial differential electrode to achieve multi parameters sensing circuit. The system is an integrated circuit design of a readout circuit for hydrogen ion, sodium ion, and temperature parameters. This research includes design of an ion-selective electrode readout circuit, bandgap reference voltage circuit, a low dropout linear regulator. The system was designed using the TSMC 0.35um 2P4M Mixed-Signal 3.3/5V process technology.
Experimental results shows that the sodium ion sensor, at pNa = 1 ~ 4, has a sensitivity of -58.3mV/pNa. The linearity is at 99.5% and the detection is limited at pNa = 3.6 (5.7ppm). It has a wide sensing range, good linearity and good reproducibility that is suitable for water quality monitoring system. The readout circuit part has achieved readout for the hydrogen ions, sodium ions, temperature and many other parameters.
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