Solution-concentration sensor using ultrasonic light diffraction effect

Describes the workings of an innovative solution-concentration sensor using an acousto-optic effect. We concentrate here on the sensitivity characteristics for NaCl and sucrose solutions over a range of ultrasonic frequencies (f/sub a/) (9-30 MHz) on which Raman-Nath diffraction occurs. The concentration of NaCl solutions (0-20.0%) has been measured with a sensitivity of 35.20 mV/% at f/sub a/=29.998 MHz, and the sensitivity for sucrose solutions (0-20.0%) have reached 13.48 mV/% at f/sub a/=29.298 MHz. Moreover, temperature sensitivity for water due to strong temperature dependence of sound velocity in liquids have reached 4.75 mV//spl deg/C at f/sub a/=9.898 MHz over the range of 25/spl deg/C/spl plusmn/5/spl deg/C. From experimental results, it was clearly confirmed that the sensitivity increases in proportion to f/sub a/ which drives an acousto-optic: (AO) cell. A proportional coefficient S/sub cf/ for NaCl solutions is 1.14 mV/%.MHz and that of sucrose is 0.341 mV/%. MHz. From that experimental results and a deviation factor derived from an empirical equation of sound velocity obtained by phase-locked loop (PLL), the sensitivity for a PLL-type AO improves 2.35 times that for an ordinary AO at ultrasonic frequency of 22.898 MHz.