Temperature effects and compensation in ultrasonic concentration measurement of multicomponent mixture

The ultrasonic technique has been successfully used to measure the concentrations of mixtures, but ultrasonic sensor is sensitive to the temperature of mixtures, which makes the ultrasonic concentration measurement very difficult. In this study, a novel ultrasonic method for compensating the temperature effects and measuring the concentrations of multicomponent mixtures comprising insoluble and soluble substances is proposed. At first, the temperature effects on the ultrasonic signals and ultrasonic concentration measurement of mixtures are investigated. Then, the stepwise temperature compensation (STC) model based on the synergy interval partial least squares (Si-PLS) model and linear interpolation as well as the global temperature compensation (GTC) model based on the Si-PLS model are separately established in combination with the ultrasonic spectra. The overall results indicate that the combination of ultrasonic spectra and temperature compensation models can compensate for the temperature effects effectively and measure the component concentrations of multicomponent mixtures in the range from 16 °C to 40 °C. The GTC model, with which the root mean square error of the prediction subset is 0.54 wt.%, is superior to the STC model, especially when the temperatures of samples are difficult to be acquired or have to be estimated from the ultrasonic spectra. The proposed method can broaden the application scope of ultrasonic concentration measurement, which makes it easier to monitor production process and product quality of multicomponent mixtures with one ultrasonic sensor only.