| 摘要 |
PURPOSE:To increase a measuring accuracy by applying a high frequency alternating voltage across a pair of electrodes arranged in a passage, comparing an extracted DC output voltage and a reference table stored in advance with each other to conduct a judgment and correcting the reference table. CONSTITUTION:An alternating voltage from an oscillator circuit 33 is applied across the casing 27 of a detector 16 and an electrode 30. The DC component of an output voltage depending on an impedance depending on solvent and soap densities is extracted by a two-stage DC current output circuit 34 and inputted to a microcomputer 36 via a level shift circuit 35. On the other hand, an output-voltage/soap-density table, control values and threshold values are stored in a ROM in a microcomputer 36 which is measuring means. An inputted output voltage and the read-out table are compared with each other and the soap density is judged in a comparing and judging device and the reference table is corrected from the calculated value of a comparison calculator and the read-out threshold values.
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