Zone C Inside Limit Alarm 
Zone C is called 1-sigma zone and is the region between zero and one standard deviation from the center line. Alarm rule 7 is triggered when multiple points (in a series) are inside upper or lower Zone C.
For alarm rule 7, the limit and length values are used for both the upper and lower charts. The data points on the chart are checked for the specified number of points in or beyond Zone C. For alarm rule 7, an alarm is triggered when there are <Limit> number of data points in the <Length> that are either in upper or lower Zone C. You can also use other alarms 40 or 41.
Features
General guidelines to detect instability within Zone C for different chart types are as follows:
Chart Type | Maximum Points to apply Rule |
|---|---|
X-Bar | 15 points in a row in Zone C above and/or below the centerline |
Individual Chart | |
Median | |
R-chart when the minimum subgroup size is 4 | |
R-chart when the minimum subgroup size is less than 4 | 10 successive points in Zone C above and/or below the centerline |
Following are the alarm properties defined for Inside Zone C Limit Alarm:
Alarm Name | Property Name | Parameter Name | Data Type | Description |
|---|---|---|---|---|
Allow Upper Chart Inside Zone C Limit Alarm | UpperWEInsideZoneCAlarmEnabled | Boolean | Enables inside Zone C alarm points for upper charts | |
Allow Lower Chart Inside Zone C Limit Alarm | LowerWEInsideZoneCAlarmEnabled | Boolean | Enables inside Zone C alarm points for lower charts | |
Alarm 7 | Limit of Inside Zone C Limit Alarm | WEInsideZoneCAlarmLimit | Integer | Sets the limits and length values to check for points that fall within Zone C |
Length of Inside Zone C Limit Alarm | WEInsideZoneCAlarmLength | Integer | ||
Alarm 40 | Limit of Upper Chart Inside Zone C Limit Alarm | WEUpperChartInsideZoneCAlarmLimit | Integer | Defines the limit and length values to check for points inside Zone C of the upper chart |
Length of Upper Chart Inside Zone C Limit Alarm | WEUpperChartInsideZoneCAlarmLength | Integer | ||
Alarm 41 | Limit of Lower Chart Inside Zone C Limit Alarm | WELowerChartInsideZoneCAlarmLimit | Integer | Defines the limit and length values to check for points inside Zone C of the lower chart |
Length of Lower Chart Inside Zone C Limit Alarm | WELowerChartInsideZoneCAlarmLength | Integer |
Example
If you define alarm rule 40 with limit and length value as 19 each, the alarm rule 40 is violated if only 19 points in a string of 19 adjacent points in the upper chart are in upper and/or lower Zone C.
Graphical representation of Inside Zone C Limit Alarm:
