| 摘要 |
PROBLEM TO BE SOLVED: To make measurable the level at high sensitivity by the multi-phase synchronous integration of a signal of echo wave, the AD conversion of obtained signal components, the moving addition, the moving difference operation, the addition and the level calculation. SOLUTION: A synchronous integrator circuit 13 extracts signal components X, Y of an echo wave according to signals of the same period as that of an ultrasonic wave emitted from a transducer 3, integrates them and extracts signal components cleared from noise signals, moving adders 172, 173 moving-add the two integrated signals X, Y respectively and remove harmonics to shape the waveform, moving subtractors 174, 175 output signals of squared difference operation values from them respectively, an adder 176 adds the two signals X, Y subjected to the moving subtraction and the square operation to provide a waveform with a peak, and a level detector 177 detects the level from the peak of this waveform. |
