Temperature-compensation factor and deviation factor of simple ultrasonic solution-concentration sensor

This paper describes a temperature-compensation factor and a deviation factor of a new simple ultrasonic solution-concentration sensor by using the phase-locked loop method (PLLM) and the phase difference method (PDM). The deviation factor is an essential specification for designing a voltage-controlled oscillator (VCO) and a phase detector (PD). It was proved that the deviation factor obtained by the empirical equation is always the same value, regardless the center frequency (f_O) of the VCO in the PLLM and the frequency of a driving oscillator (f_D) for a transmitter in the PDM. The deviation factor in the 20-30°C temperature range for 0.0-1.0% NaCl and 0.0-5.0% sugar solutions of the PLLM is 1.61×10^-3/°C and 1.68×10^-3/°C. Moreover, it has become clear that the same temperature compensation factor can be used for both the NaCl and sugar solutions deriving from their equations