PLC | contact input selection? A Contact (NO), B (NC)
A contact (NO), B contacts (NC), the use of that too!?
Generally not often encountered in the switch, but important, such as emergency EMS, the limit to protect the switch.
Will use the B contact.
So the signal remains live. If the line cut off, will know immediately.
Also coupled with a line check function.
Other detector signal, the A contact can be used.
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Some special cases:
Such as the minimum level detector,
Because the level is usually more than the lower limit position, it will always know to check.
If we use B contact, but no signal has been lost protection.
So the use of contact A, so that in the normal level, the lower limit, or has been output.
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