Important Definition In PLC :- SCAN TIME & SCAN CYCLE

SCAN TIME :-

Scan Time is nothing but the time taken by the processor to sense first input of the program and execute last output of the program.
The unit of Scan Time is Bits/Sec.

SCAN TIME depends on :-

no. of I/O's.(scan time ∝ no. of I/O's)
Length of Program.(scan time ∝ Length of program)
Speed of Process.(scan time ∝1/speed of process)

scan time is directly proportional to the no of I/O's, if program has more no of I/O's then it take relatively more time.
scan time is directly proportional to the length of program, more the length processor will take more time to execute the program.
and finally scan time is inversely proportional to the speed of the processor, more the speed less it will take time to execute the program.

SCAN CYCLE :-

"SCAN CYCLE is the cycle of Input Updation, Program Execution, & Output Updation of one Input and it's Output."

below fig shows the graphical representation of Scan Cycle :-
⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨⧨

Scan cycle.

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