| 摘要 |
PROBLEM TO BE SOLVED: To stably and easily measure a difference of elevation in each measuring point, without lengthening total pipe length, without increasing the water amount for stabilizing water temperature, and without prolonging the time for water level measuring cycle. SOLUTION: A water conveying pipe 33 of which the one end is connected to the lower part of a reference water tank 32 is arranged along a sloped face of the ground, and three-way solenoid valves 35a-35d are provided in connection parts of the water conveying pipe 33 with branch pipes 34a-34d for connecting lower parts of respective measuring water tanks 31 to the pipe 33. By this manner, when the water level of the water tank 31c, for example, is measured, the three-way solenoid valve 35c corresponding thereto is switched to the branch pipe 34c side, so as to eliminate the influence of a negative pressure acting on the water conveying pipe 33 on the upper side of the three-ay solenoid valve 35c, and the water level in the measuring tank 31c can be thereby stabilized quickly.
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