A surface acoustic wave device for water impurity levels monitoring by measuring signal-to-perturbation ratios

摘要

This paper reports a novel method for water impurity levels monitoring by measuring the signal-to-perturbation ratios (SPRs) of the surface acoustic wave (SAW) device. It has been shown that when a droplet is put on the SAW propagation surface, the SAW is attenuated and there will be a signal shift after the evaporation due to surface perturbations caused by impurity residues. For cleaner water, the SAW propagation surfaces are clean after the evaporation which cause smaller signal shifts or perturbations and then generate higher SPRs. However, for dirty water, the sensor SPRs are lower because of more impurity residues. Besides, the sensor detection performance has been compared with the total dissolved solids (TDS) meter. The results indicate that the average SPR of the SAW sensor presents a good linear response to the NaCl impurity content in lower concentration ranges of 100 to 1000 ppm similar to the TDS meter. (C) 2019 The Japan Society of Applied Physics