Publication 1747-RM001G-EN-P - November 2008
2-8 Basic Instructions
Timebase
The timebase determines the duration of each timebase interval. For Fixed and
SLC 5/01 processors, the timebase is set at 0.01 second.
Timer Accuracy
Timer accuracy refers to the length of time between the moment a timer
instruction is enabled and the moment the timed interval is complete.
Inaccuracy caused by the program scan can be greater than the timer timebase.
You must also consider the time required to energize the output device.
Timing accuracy is -0.01 to 0 seconds, with a program scan of up to 2.5
seconds. The 1-second timer maintains accuracy with a program scan of up to
1.5 seconds. If your programs can exceed 1.5 or 2.5 seconds, repeat the timer
instruction rung so that the rung is scanned within these limits.
EXAMPLE
If the timer base is set to 0.01, it would take 100
counts as the preset value (PRE) to equal 1 seconds
worth of timing.
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