Trend Limit Alarm 
Trend Limit alarm rules are triggered when multiple points are in the same direction (either increasing or decreasing).
For alarm rule 3, the limit and length values are used for both the upper and lower charts. The data points plotted on the chart are checked for the specified number of increasing (or decreasing) points. An alarm is triggered when there are <Limit> number of data points in the <Length> data point string that are either all increasing or all decreasing. You can use alarm rules 28 and 29.
Features
Following are the alarm properties defined for Trend Limit Alarm:
Alarm Name | Property Name | Parameter | Data Type | Description |
|---|---|---|---|---|
Allow Upper Chart Trend Limit Alarm | UpperWETrendAlarmEnabled | Boolean | Enables trend limit alarm for upper chart | |
Allow Lower Chart Trend Limit Alarm | LowerWETrendAlarmEnabled | Boolean | Enables trend limit alarm for lower chart | |
Alarm 3 | Alarm Limit of Trend Limit | WETrendAlarmLimit | Integer | Sets the limits and length values to determine the alarm |
Alarm Length of Trend Limit | WETrendAlarmLength | Integer | ||
Alarm 28 | Alarm Limit of Upper Chart Trend Limit | WEUpperChartTrendAlarmLimit | Integer | Sets the limits and length values to check for increasing or decreasing data points on the upper chart |
Alarm Length of Upper Chart Trend Limit | WEUpperChartTrendAlarmLength | Integer | ||
Alarm 29 | Alarm Limit of Lower Chart Trend Limit | WELowerChartTrendAlarmLimit | Integer | Sets the limits and length values to check for increasing or decreasing data points on the lower chart |
Alarm Length of Lower Chart Trend Limit | WELowerChartTrendAlarmLength | Integer |
Example
If you define alarm rule 28 with limit and length as 7 and 8, the rule is violated when 7 points in a string of 8 adjacent data points are either all increasing or all decreasing. In the illustration below, all the 7 points are increasing and therefore marked as a rule violation.
Graphical representation of a Trend Limit Alarm:
