Through the scan time changes according to the size of the program and type of instructions used in the program, you should bear in mind that the longer (more complex) a ladder program is, the longer the scan time will become.
Ladder programs process input processing at the beginning of a scan and output processing at the end of a scan. For this reason, when the scan time becomes longer, it takes more time to process the data (ON/OFF states of sensors and switches, numerical values such as pressure, encoder or temperature) obtained by input processing and output the result. The shorter the scan time becomes, the more accurate processing becomes possible as the PLC’s response (processing time from input through to output) improves.
For examples, when the PLC scan time is 100ms per scan, it only manages to take 100 times measurement in 10 seconds. While for the PLC scan time is 10ms per scan, it can manage to take 1000 times measurement in 10 seconds. Conclusion is that with the shorter scan time allows data to be measured closer to real time.
To shorten the scan time
•Set so that only the required programs are executed at all times by a program using modules/macros.
•Try to use only exclusive commands to make the entire program compact.
•Try not to use instructions such as FOR to NEXT that are processed countless times in a scan.
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