Create an SQC analysis

Identify the Statistical Quality Control (SQC) pattern tests that you wish to use. See Understand Statistical Quality Control (SQC) analyses for more information.

1. In the navigator, click Elements.

2. In the Elements browser, select the element where you want to create the analysis.

3. In the viewer, click the Analyses tab.

   The tab lists any analyses already defined for the element.

4. Create a new analysis for the element:

   • If no analyses exist, click Create a new analysis to create the first one.

   • Otherwise, click New Analysis to create a new one.

5. Enter information to identify the analysis:

   • Name

     The name that uniquely identifies this analysis.

   • Description

     Optional text that describes the analysis.

   • Categories

     Optional category that you can assign to the analysis. Click the list and select the check box next to categories you want to assign or click New to create a new category.

   • Analysis Type

     Click SQC.

6. Provide the inputs for the SQC pattern test. All these inputs should be attributes or attribute templates previously defined in your PI System.

   1. In the Source field, select the PI AF attribute or attribute template that provides the data for the pattern test.

   2. In the Upper Control Limit and Lower Control Limit fields, select the PI AF attribute or attribute template that provides the largest and smallest limits on the dimension of the data being tested.

   3. In the Center Line field, select the PI AF attribute or attribute template that provides the normal or ideal value of the data.

7. Choose the output of your analysis as either Event Frame or AF attribute.

   If you choose Event Frame, select an event frame template. If you choose AF attribute, you can either choose from a list, or create a new attribute. SQC Analysis rule automatically creates an enumeration set named SQC Enumeration. This enumeration set has the same values used in Data Archive SQC DigitalState set so that continuity with existing Data Archive is preserved. SQC Enumeration is created when: 1) you map the output to a new AF attribute, 2) this or another enumeration set with the required name and values does not already exist and 3) you have the right to create enumeration sets.

   AF attribute output defaults to a string attribute if the aforementioned conditions are not met.

8. Optional. Generate a root-cause event frame for every event frame that the analysis generates.

   A root-cause event frame captures asset data, which can help you analyze conditions just before the start of the event frame.

   1. From the Advanced Event Frame Settings menu, select Generate Child Root Cause Event Frame Before Parent Event Frame Starts .

   2. In the Duration field, enter the length of the root-cause event frame.

      The root-cause event frame starts this long before the generated parent event.

      Note: The root-cause event frame is created only for the first instance, not for each time that the trigger is True.

9. Optional. Map a start trigger name and start trigger expression to an event frame attribute.

   1. From the Advanced Event Frame Settings window, select Save start trigger name to event frame attribute and then select an attribute or attribute template on the event frame template to which the start trigger name is saved.

   2. From the Advanced Event Frame Settings window, select Save start trigger expression to event frame attribute and then select an attribute or attribute template on the event frame template to which the start trigger expression is saved.

      The start trigger name and start trigger expression can now be seen on generated event frames, on the selected attributes.

10. Enter SQC pattern test information.

    1. Select the check box for each SQC pattern test that you wish to apply to your data.

    2. In the X of Y column, select appropriate numerical values for X and Y for each selected pattern test that requires this input.

       Specify the number of values X out of a number of sampled values Y that can be above or below the corresponding pattern test limits.

       Patterns (X and Y values) suggested by Western Electric are shown by default.

       Note: X may not be greater than Y.

    3. Select the Limit as Above, Below or Both, for each selected pattern test.

       By default, tests are applied on both sides of the center line.

11. Optional. Select the ClearOnControlLimitChange check box.

    With ClearOnControlLimitChange selected, if any of the control limits changes, asset analytics resets the state of a running SQC calculation, and the SQC calculation is restarted with the changed values. In addition, associated open event frames are closed before the calculation is resumed.

    With ClearOnControlLimitChange not selected, the calculation simply proceeds using the changed values for the control limits.

    If all selected SQC tests pass, the Output Value field displays "Normal". If some tests fail, the Output Value field shows the highest priority test that failed. Changing any of the SQC inputs will clear the Output Value field.

12. Optional. Click Evaluate to verify the output values at both Value at Last Trigger and Value at Evaluation times. If all selected SQC tests pass, the Output Value field displays "Normal". If some tests fail, the Output Value field shows the highest priority test that failed. Changing any of the SQC inputs will clear the Output Value field.

13. Click Check In on the toolbar.

    PI System Explorer saves and checks in your analysis, and then starts running the analysis.