List and explain the different counters of PLC in detail.

1 Answer

Answer :

A counter in PLC is an instruction equivalent to mechanical counter. A counter block of PLC has two control inputs, Count line and Reset line. When count line makes FALSE-to-TRUE transition, the counter increments/decrements its accumulated value by 1. FALSE-to-TRUE transition on reset line resets the accumulated count to zero. The common format of counter instruction of PLC is shown in following figure. 

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Commonly used counters used in PLC are 1) UP Counter 2) DOWN counter 3) UP-DOWN Counter The counter operation is shown with the help of timing diagram of an up-down counter which is combination of up and down counter. The up-down counter has three inputs, count up, count down and reset.

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