A fluid sensor based on the surface transverse wave (STW) delay line on ST-cut quartz has been developed and tested in a large number of fluids with different viscosity and permittivity levels.Influence of fluid mechanical and electrical properties on the sensor’s response has been determined and the sensor’s performance has been compared with a bulk acoustic wave (BAW) viscosity sensor.The result shows that the viscosity sensitivity of the developed STW sensor represented by the signal to noise ratio is lower than that of a 5 MHz BAW sensor.Applications of the sensor in detecting the quality of industrial fluids are discussed. A fluid sensor based on the surface transverse wave (STW) delay line on ST-cut quartz has been developed and tested in a large number of fluids with different viscosity and permittivity levels. Fluid effect and mechanical properties on the sensor’s response has been determined and the sensor’s performance has been compared with a bulk acoustic wave (BAW) viscosity sensor. The result shows that the viscosity sensitivity of the developed STW sensor represented by the signal to noise ratio is lower than that of a 5 MHz BAW sensor. Applications of the sensor in detecting the quality of industrial fluids are discussed.