This example demonstrates how the No Change feature can be used to check whether a counter point has changed by a specific amount during any 30-minute period.
Example - No Change in Absolute Value:
A counter point is configured with these No Change properties:
Type: Absolute
Deadband: 5
Interval: 30M
Severity: Alarm, Low priority.
ClearSCADA will only deem the point value to have changed if its value changes by more than 5, over a 30-minute Interval.
Whenever the value does change by more than 5, ClearSCADA restarts its No Change checking process for the point.
If the point value does not change by more than 5 for over 30-minutes, ClearSCADA will raise a low priority alarm to indicate that the point has not changed sufficiently. ClearSCADA will also restart its No Change checking process for the point.
In this example, the counter’s value changes as follows:
| Time | Value | Comments |
|---|---|---|
|
09:05:00 |
24 |
ClearSCADA starts its No Change checking process. It uses this time for the start of the Interval, and compares future values against this value to see whether they change by more than the Deadband of 5. |
|
09:10:00 |
25 |
|
|
09:15:00 |
27 |
|
|
09:20:00 |
30 |
As the value has changed by 6 (which is more than the Deadband) in the previous 15 minutes, ClearSCADA re-starts its checking process. It uses the new time and value as the basis against which to perform those checks. |
|
09:25:00 |
30 |
|
|
09:30:00 |
30 |
|
|
09:35:00 |
30 |
|
|
09:40:00 |
31 |
|
|
09:45:00 |
32 |
|
|
09:50:00 |
32 |
|
|
09:55:00 |
33 |
As the value has only changed by 3 in the last 35 minutes (and as such, has remained within the Deadband for longer than the specified Interval), ClearSCADA raises a No Change alarm. It also re-starts its checking process, using the new time and value as the basis against which to perform those checks. |
|
10:00:00 |
36 |
|
|
10:05:00 |
40 |
As the value has changed by more than the Deadband of 5 in the last 10 minutes, ClearSCADA clears the No Change alarm and re-starts its checking process. It uses this time and value as the basis against which to perform its checks. |
|
... |
Further Information
Configure the No Change Properties for an Analog or Counter Point.