Abstract
Detection of water content in hydraulic oil is critical to identify abnormal wear conditions for purpose of predicting possible machinery failure in hydraulic systems. The paper reports a feasibility study of measuring the water content in the hydraulic oil using a ZnO thin film surface acoustic wave (SAW) device combined with the standard distillation method. The shift of resonant frequency of the SAW device increases with the increase of water content in hydraulic oil, and reaches 919 kHz for 0.80 wt% water content in oil samples. The results indicate that the ZnO SAW sensor can detect water content in hydraulic oil with high sensitivity.