| A novel triple-channel Shear-Horizontal Surface Acoustic Wave (SH-SAW) liquid detection system based on 36-YX LiTaO3 was developed in this research. The sensor was mainly designed to detect liquid conductivity in order to determine the concerntration of heavy metal in water.The SH-SAW sensor consists three delay lines whose working frequencies are 52.75 MHz. One channel is metally shorted, another is electronical opened, and the third one is coated with chalcogenide glasses to improve its sensitiviy to Fe3+ By applying silicon rubber seal ring and resin liquid cell, the sensor is able to work in liquid.The application of Flow Injection Analyze (FIA) techonique not only enables the system work automatically, but also improves its reproducibility. Further more, this techonique also supplies time information in detecion, by using Partial Lest Square (PLS) algorithm, we are able to disern ion ration in binary mixture solution.Results show that the stationary response of sensor expresses the liquid conductivity (error<0.24%); the lower detection limit is 1 .8 X 10-4 S/m, according to the electrolytes' concentration between 10-4~10-6 mol/L; the slope of transient response denotes the ratio of binary mixture with PLS method (error<3%); chalcogenide glasses film can improve the lower detection limit of Fe3+ for about 1 order. The system can also detect alcohol concentration (error< ±0.2 Deg) and water ratio in organic solutions (error<±l%). This novel sensor system exhibits high stability and reproducibility (<10Hz).The instrument was designed by morden instrument science, with the combinaition of high frequency analog circuit, DSP system and PC software programming. This novel sensor system shows merits of high sensitivity, good stability, reproducibility, anti-interference, rapid response, small size (30 X 20 X 20cm3) and easy to use. It is a suitable system for in-Situ liquid detection.
|
PDF Full Text Request