Temperature-compensation circuits for simple solution-concentration sensor with temperature compensation using bulk acoustic waves

This paper describes the use of a temperature-compensation circuits for simple solution-concentration sensor with temperature compensation using bulk acoustic waves. We analyzed the design method of temperature-compensation circuit (TCC) in order to eliminate considerable effect temperature has on sound velocity in liquids. The design methods are derived on a temperature-compensation factor by using a Taylor series expansion of the equation for sound velocity, which is a function of concentration and temperature centered on a reference concentration and reference temperature. The phase-locked loop (PLLM) was applied to NaCl solutions of varying concentrations and shown to yield an accurate determination of concentration within +/- 0.024% independent of variations in temperature of +/- 1.3 degrees C at approximately 25.0 degrees C.