| 摘要 |
PROBLEM TO BE SOLVED: To detect immediately parts having an abnormal function due to short circuit by producing constructively an alarm when a resistance value between a power source line and a common line of a printed circuit board is reduced less than a fixed threshold value. SOLUTION: A power supply pin and common pin of a probe 20 are mounted to proper sockets on a printed circuit board 1, for example the socket or the like having not parts packaged. SeveralμsV voltage is supplied between the power source pin and the common pin from the power source 22 of a low voltage power source to measure a resistance value of current flowing in a circuit 21 with a resistance meter 23. When the measured value exceeds a fixed limit value, i.e., when a short circuit happens inside and outside parts mounted to the board 1 between a power source line and a common line, the measured value is lowered abruptly to 0-10Ωso that an alarm 24 produces an alarm source from a buzzer 24.
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