| 摘要 |
PURPOSE:To detect whether a contact to be detected is in the make state or in the blake state while floating the contact from ground by terminating the primary winding of a transformer by the contact to be checked and connecting an AC power supply to the secondary winding of the transformer via a resistor. CONSTITUTION:The contact 1 to be checked is connected to the primary winding of the transformer 10 and isolated completely from ground. When the contact 1 is in the brake state, the impedance viewing the contact 1 to be checked from the secondary wining of the transformer 10 with respect to an output frequency (f) of an oscillator 11 is very high and the impedance is very low when the contact 1 is in the make state. Thus, the output of a rectifier circuit 13 is connected to a positive input terminal of a comparator 14, a reference voltage +Ec is fed to a negative input terminal of the comparator 14 and then they are selected as +Ed>+Ec>0, an output OUT of the comparator 14 goes to 'H' when the contact 1 to be checked is in the brake state and goes to 'L' when in the make state, thereby detecting the state of the contact 1 to be checked easily.
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