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TON SFB4

Created by: big_muzzy at: 4/21/2010 2:27 PM (2 Replies)

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4/21/2010 2:27 PM	Rate (0)
big_muzzy Posts: 48 Rating: (0)	Hi Masters! Can anyone advise me how TON SFB4 measures the time? The instance data block holds two time values - one storing beggining of counting?? other actual time?? I understand how measurement takes the place generally. I checked system time, system tick but any of those values do not match those held in instance DB. On top of that system tick is non-retentive. My concern is related to situation when you update the system clock - can the update affect the operation of the TON in any way?? I have tested TOF as well and I found that both functions uses the same value as free running time but where is it stored? Regards!!
big_muzzy Posts: 48 Rating: (0)	Last edited by: big_muzzy at: 4/21/2010 3:10 PM
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4/22/2010 8:44 AM	Rate (1)
yy1 Gold Member Joined: 3/24/2009 Last visit: 7/9/2024 Posts: 535 Rating: (112)	Dear big_muzzy, you are right, the times in the instance-DB are not accected by the system-time. The time at the PT-input tells the block how long a rising edge at the IN-parameter should be delayed. At the ET-output you can see the time that has passes since the last rising edge at the IN-input. In the attachment you can see a detailed description from the block-help. I hope this helps. Best regards, yy1 Attachment SFB4.JPG (403 Downloads)

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4/26/2010 9:57 AM	Rate (0)
big_muzzy Posts: 48 Rating: (0)	Many thanks for your reply! Right! I have tested that and fine - you are right. Even change of PLC time didn't affect the timer. Does anyone know what time register TON is accessing for reading actual time? I need to make the timers which work in very similar way to TON thus that question. Mentioned register is retentive and not affected by change of PLC time, 1ms resolution. I tried TIME_TICK but it is not retentive. Or is that Siemens only know-how?
big_muzzy Posts: 48 Rating: (0)
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This contribution was helpful to 1 thankful Users yy1

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