| 摘要 |
PROBLEM TO BE SOLVED: To accurately measure specific gravity of a treating liquid continuously without controlling a liquid level in a specific gravity measuring vessel. SOLUTION: A high-pressure receiving housing 26 and a low-pressure receiving housing 40 are attached, with 1000 mm of level difference, to the measuring vessel 18 to which an etchant L of a specific gravity measuring object is fed. A differential pressure corresponding to the level difference 1000 mm is detected by a differential pressure transmitter 30, resulting from a difference between liquid pressures applied to the both housings 26, 40. A computing part 46 computes the specific gravity of the liquid based on the differential pressure and the level difference. A reference water is not required as is required in a conventional specific gravity measuring instrument. The specific gravity is thereby measured accurately and continuously since free from water level fluctuation of the reference water and temperature fluctuation of the reference water. Specific gravity measurement is not affected substantially by fluctuation of an etchant flow rate because the flow rate of the etchant L to the measuring vessel 18 is not required to be held constant.
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