| 摘要 |
PROBLEM TO BE SOLVED: To continue pump operation to a lower water level by carrying out pump operation serially or after a pump is started serially until a water level reaches to a low level before suction of water is started by a single or a plurality of pump(s). SOLUTION: A current signal from a pump is obtained by a current transformer A, one of the leading wire of a pump motor is taken out passing the current transformer A. The current signal is rectified in a first step B, and treatment is carried out in a low range filter C of a three step cascade condition. A signal is amplified by an amplifier D so as to match to the level of a processor. A rotary switch E is used due to set a cycle number of pump stop per day, and the cycle is read in by a micro processor for exchanging into the time of a pump cycle. It is thus possible to continue pump operation to a low water level, and also it is possible to eliminate dangerousness of sewage collection caused operation stop.
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