| 摘要 |
PURPOSE:To surely perform the detection of water level and short circuit regardless of the level of specific resistance by connecting a first transistor whose base is connected to a water level switch to the water level detecting and setting circuit in a comparator, and a second similarly connected transistor to the short circuit detecting and setting circuit. CONSTITUTION:A first transistor Q1 whose base is connected to a water level switch 3 is connected to the water level detecting and setting circuit which sets the input voltage to one of input terminals of a comparator CP, and a second similarly connected transistor Q2 is connected to the short circuit detecting and setting circuit of the other input terminal. By this constitution, when the water level is to be detected by the water level switch 3, the electric current flowing to the water level detecting and setting circuit also flows to the second transistor Q2 connected to the short circuit detecting and setting circuit. Then, by the amplification action of the second transistor Q2, the definition level of short circuit detection is improved, and so, the water level and short circuit are differentiated for sure detection even with circulation water having a low specific resistance.
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