Title:
CIRCUIT FOR DETECTING CHANGE OF RESISTANCE VALUE
Document Type and Number:
Japanese Patent JP3039349
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To keep the safety by providing a pulse generating means which generates a continous pulse when the safety side is detected, and generates no continuous pulse when the unsafety side is detected.
SOLUTION: When a detection terminal L detects the presence of water (safety side), a resistance between the terminals L and E is around zero and the potential of the terminal L is low. Therefore, when a half cycle of positive AC is applied to a terminal A, a phototransistor F1 is energized and a waveform at an output end 1 is formed by a resistance R5 and an invertor IV1, then a continuous pulse is outputted from an output end O, and it is inputted into a judgment means CP, which is judged as presence of water. On the other hand, when the terminal L detects the absence of water (unsafety side), a resistance between the terminals L and E is almost infinite and a potential at the terminal L is high, so the phototransistor F1 is not energized. Therefore, no pulse is outputted from a pulse generating circuit P. Further, even when any failure occurs in a circuit, no pulse is outputted from the circuit P, which is judged as absence of water.
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Inventors:
Eiji Tasaka
Yasushi Takubo
Yasushi Takubo
Application Number:
JP35386895A
Publication Date:
May 08, 2000
Filing Date:
December 28, 1995
Export Citation:
Assignee:
Miura Industry Co., Ltd.
International Classes:
G01F23/24; (IPC1-7): G01F23/24