| 摘要 |
PROBLEM TO BE SOLVED: To eliminate the need for installing an insulation power circuit that should be provided for each input point by constituting a circuit with a relay for insulating against input from an external voltage generation source, a capacitor for retaining an input voltage value, and a Zener diode for outputting a voltage which exceeds a normal input range voltage to an operation amplifier. SOLUTION: Capacitors 4-6 retain the generated voltage of an external voltage generation source, and relays 7-12 connect the generation voltage of the capacitor to a next-stage circuit when they are on, and insulate an internal circuit from an external one when they are off. When they are on, the retention voltage of a capacitor 13 is transferred to an operation amplifier 18. When they are off, relays 14 and 15 insulate the operational amplifier 18 from the capacitor 13. Then, when one of connection parts 41 and 42 between a voltage generation source 1 and an input circuit 20 is burned out, since a capacitor 4 retains the generated voltage of a Zener diode 21, burnout is discriminated when after the retention voltage of the capacitor 4 is read, the voltage value is not normal but is equal to the generated voltage of the Zener diode 21.
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