Scan time calculation

rajsingh85

Member
Join Date
Mar 2007
Location
DELHI
Posts
2
Dear All,

I m a new in PLC line and had started working in this field just before 3 months..Can anyone suggest me how to calculate a scan time of any PLC..is there any mathematical formula or by some other method I can calculate scan time.
I m working on S7-300 PLC..kindly help.
 
Most PLC manufacturers publish execution times for each instruction in the function set.

My personal opinion is that unless keeping the scan time at or below some specified time is crucial to the success of the project, don't waste your time trying to calculate it. Use the time you would have spent calculating it to design an efficient program structure. Then write your logic and see what the scan time turns out to be.
 
scan time of s7- 300 various with ur programming length... u can see the scan time of the s7 300 plc by

simatic manager-----> plc ---> module information ----> scan time... this is possible only when online with S7 300 plc normally it various from 8 msec to 10 msec
 
PLC Scan time

Dear All,

Still I didn't get any proper answer related to scan time..please suggest.
or can any1 provide me any link where I can found these type of things.
 
To calculate the scan time, you must add the execution times of each instruction in the program. To that, you must add the time it takes for the PLC to update the data from the I/O modules, the time to service any communications requests from external devices, and the time for any other functions specific to the particular application.

You have to have a program written before you can calculate the scan time. That's why it's usually more efficient to download the program to the PLC and see what the scan time actually is rather than spend time trying to calculate what it will be.
 
Note also that you must take into account any instructions that are present inside a loop - you will need to know how many times the loop is executed.
 

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