Access an SPC Chart

Before you begin

  • In the variable definition in Plant Applications Administrator, specify the type of the SPC chart that you want to see for the variable. For instructions, refer to the Configure and Run the SPC Chart topic in Proficy Plant Applications Help. If you do not configure an SPC chart for a variable, the SPC chart will not appear.
  • When you configure the autolog sheet, place all the variables and subgroup variables with SPC configuration in the correct sequence (that is, do not place the variables without SPC configuration in between the ones with SPC configuration). The following table provides an example for the correct sequence and the incorrect sequence.
    Variable Configured for SPC Charts? Correct Sequence Incorrect Sequence
    Motor torque (main variable) Yes
    • Motor torque (main variable)
    • Motor rpm
    • Motor current
    • Motor power
    • Motor length end-to-end
    • Motor torque (main variable)
    • Motor rpm
    • Motor length end-to-end
    • Motor current
    • Motor power
    Motor rpm Yes
    Motor current Yes
    Motor power Yes
    Motor length end-to-end No
  • If you want alarm notifications to be plotted on the SPC chart, configure alarms for the SPC chart. For instructions, refer to the Configuring Alarms topic in Proficy Plant Applications Help.

Procedure

  1. Access the autolog history of the activity for which you want to access the SPC chart.
  2. Select .
    The button appears only if at least one variable in the activity is configured for SPC charts.
    Depending on the type of the SPC chart configured for the variable, one of the following charts appears:
    • X-Bar and Range
    • X-Bar and Sigma
    • X-Bar and Moving Range
    • P chart
    • U chart

    If a variable is configured with other SPC variables, its value will not be plotted on the SPC chart.

    The following table describes each chart.
    Chart Type Description
    XBar Plots the average of the variable values for each subgroup, indicated by the black line. In addition:
    • The red dotted lines indicate the calculated upper and lower control limits for the variable.
    • The blue dotted line indicates the average of the XBar values for all the 30 samples for the variable.
    The serial names for the red and blue lines appear in the legend.
    Note: By default, values for the last 30 samples appear in the chart. You can, however, change this value by setting the numberOfSamplePoints property in the app.properties.json file. If you have installed Plant Applications Web Client using Docker, this file is located in the Plant Applications installation folder/PlantApplicationsDocker/plantapps-universal-client/activities folder. Otherwise, this file is located in the <Plant Applications installation folder>\PlantApplicationsWebClient\NodeUIApp\activities-app\assets folder.
    Range Plots the difference between the maximum and minimum values in a subgroup.
    Sigma Plots the standard deviation of the values in a subgroup.
    Moving Range Plots the range calculated between the current and previous data points in a subgroup.
    P Chart Plots the fraction of the non-conforming items in a subgroup. This chart is used for subgroups of varying sizes and with pass/fail or yes/no type of variable values (for example, tests conducted using a go-no-go guage).
    U Chart Plots the number of non-conformities per item in a subgroup (for example, a scratch, dent, or a bubble). This chart is used for subgroups of varying sizes.
    If alarms are configured for one or more values, and if the value is beyond an acceptable limit, the value is indicated by a color-coded indicator in the SPC chart, representing an alarm. The color of the indicator depends on the priority of the alarm. For information, refer to Acknowledge an Alarm Notification.

    When you pause over a value on the SPC chart, a tooltip appears, displaying the SPC variable name, the event number, end date and time of the event, data point, xlcl, xucl, and xcl of the main variable for which the SPC chart is plotted. For an alarm, the alarm description also appears.

    The SPC charts appears inline with the variables whose values are plotted on the chart. Variables that are not configured for an SPC chart appear below the SPC variables and the chart.

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