Abstract
In the area of the fluidic measurement by the use of ultrasonic wave propagation, the existence of gas bubbles in liquid causes some trouble, due to scattering and absorption of the wave.
A new method for non-contact detection and measurement of bubbles in blood is developed utilizing the same phenomena.
In this paper, a new apparatus for the measurement is described. Its theoretical analysis on the attenuation of ultrasonic wave in two-phase fluid is also discussed. Two different implementation are tested, these are, (1) the measurement through the average attenuation of the transmitted wave, (2) the measurement through the RMS fluctuation of the wave power. As the results of the experiment, the theory was verified and the method was proved to be promising. The minimum detectable concentration of bubbles is 100ppm.
Our development work was aiming at the detection of small bubbles in human blood during the dialysis treatment. In this application the vantage of this method is fully demonstrated, which employs highly sensitive instruments not in direct touch with blood. Some results of field trial in a hospital are given. Also, a possible application to the industrial measurement is mentioned.
