Development of simple apparatus for measuring liquid-concentration by ultrasonic light diffraction effect

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We developed a measuring apparatus which has the absolute value for a sensitivity of the tracker voltage ,i.e., 35.3m V/ % at the driving ultrasonic frequency of 29.998 MHz using Raman-Nath diffraction effect owing to measure the concentration of the NaCl and saccharose solutions as liquid specimens. A summary of the other achievements is shown below.1. In the case of measuring the concentration for the 0.0-1.0 % NaCl and 0.0-5.0 % sugar solution, its measuring system may be designed using a deviation factor of 0.0078.2. Moreover, it became clear that the same temperature-compensation factor can be used for both the NaCl and sugar solutions deriving from the empirical equations of sound velocity. Specifically, its value in a 0.0-1.0 % NaCl solution at f_o=2.15 MHz for the PLLM is 3.381 kHz/℃, and that in a 0.0-5.0 % sugar solution is 3.379 kHz/℃ within the range of 25℃ ±2℃.3. The basic measuring values are obtained by the use of measuring apparatus which is equipped on the simple steel experimental optical tables without the vibration isolation mechanism4. There is no necessity for using always the glass plate for the transmission plane of the AO cell. The acrylic plate is enough suitable for the transmission plane for light at the cell.5. The most suitable value for the distance between the vidicon camera tube and the bright spot on the screen at the iris diaphragm is 30〜100mm to measure extreme sensitively the tracker voltage at the frequency used Raman-Nath diffraction effect.6. A temperature-compensation circuit is necessary due to the frequency proportional coefficient for the temperature sensitivity S_<tf> = 0.201 mV/ ℃.・MHz.7. From the experimental results and the deviation factor derived using the empirical equation of sound velocity obtained by the phase-locked loop ( PLL ), it was found that the sensitivity for the PLL-type AO improves 2.35 times that for an ordinary AO at f_a = 22.898 MHz.