Interval and Offset

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Certain tag types support Interval and Offset fields to define when and how often a timed activity occurs. Examples of timed activities include:

Interval and Offset fields are specified as Duration Literals. For example T#1m30s represents 1 minute and 30 seconds.

Timed Activity Frequency

The Interval field defines how often the activity occurs. For example an Interval of T#5s specifies the timed activity occurs every 5 seconds.

Fernhill SCADA will attempt to perform the timed activity at the specified interval. However Fernhill SCADA does not guarantee the timed activity is performed at this interval. External and internal influences such as computer load, and the response time of external devices, may result in timed activities being delayed or dropped.

When a Timed Activity Occurs

Both the Interval and Offset fields define when a timed activity occurs:

  1. The current time is rounded up to a multiple of the Interval. This is the base time of the timed activity.
  2. The Offset is added to the base time.


Some examples of timed activity:

IntervalOffsetCommentTypical event times
T#500msT#0sEvery 500 ms at the start of second and at the start of the second plus 500ms12:43:00.000
T#500msT#250sAs above, but offset by 250ms12:43:00.250
T#10sT#0sEvery 10 seconds at the 10 second boundary12:43:00.000
T#10sT#5sAs above but offset by 5 seconds12:43:05.000

Further Information

Duration Literals

To learn about duration literal values.


For the meaning of terms used in Fernhill SCADA.