Starting the Control
In PI Vision, click on "Assets" at the top left to expand the corresponding area.
In the upper area click on "weruSPCTrend" to select the control.
Then you can search for the desired PI tag and add it to the display using Drag&Drop.
Functionality of the Control
The Control shows in a trend view all data points within the configured time range.
Background Color
The thin black line in the center indicates the average value, unless a value other than "Center Line" has been specified in the configuration. Each color gradation up and down corresponds to one sigma of deviation. At +/- 3 sigma, a thin blue line is visible and the corresponding value is plotted on the right y-axis.
Configuration
Alarms
There are 7 different alarm types, each of which can be customized in the configuration. Each one can give an indication of anomalies in the data so that it can be reacted to at an early stage. Once the alarms have been activated in the configuration, it is possible to adjust the given parameters per alarm. As soon as a data point fulfills one of the activated rules, it will be displayed with the stored symbol instead of just a small black dot in the control. If more than one rule applies to a data point, the rule that is the highest in the list will be displayed (for alarm 1 and 3 at the same time, a red circle will be displayed).
Plot Time
Here you can select whether all data points are used that are in the time range of the PI Vision display or statically the last n data points are used that were recorded before the end date.
Chart Type
The following types of SPC control can be displayed: Individuals, Average. The control handles the available data points as follows, depending on the configuration:
Individuals: It works directly on the raw data. Each data point in the PI system is considered individually and displayed in the control.
Average: If the chart type is changed to Average, the sample size must also be configured between 2 and 25. Subsequently, 2 to 25 data points are combined to one data point in order to display an average value. This is then displayed in the control and used for further calculations.
Limit Calculation
Within Sigma Calculation, you can select which formula is to be used to calculate Sigma. Average Range Estimate and Average Standard Deviation Estimate are available.
Average Range Method:
Sigma is calculated as follows:
The Average Moving Range is calculated using:
Average Standard Deviation Method:
Sigma is calculated as follows:
The Average Standard Range is calculated using:
Under Center Line, another value can be defined as the center line instead of the average. Upper and Lower Control Limit define the value of +/- 3 Sigma. Upper and Lower Specification Limit have no influence on the calculations and define the specification limits and are displayed with dashed lines in the Control.
With an activated checkbox "Hide Title" the title containing the name of the PI tag is no longer displayed and hidden.
Removing the Control
Before removing the control it is necessary to switch into edit mode (Icon in the upper right corner). Thereafter it is possible to click on the control and press the delete key to remove the control.