You can create statistical trends for your machine attributes using one or more Nelson Rules. These may help you analyze the consistency and predictability of your attribute values.
Trends use a set of Nelson Rules along with your machine type and attribute to be analyzed. For example, you may wish to analyze the trends for the pressure, temperature, or vibration sensor values of your machine. You can choose one or more of the following Nelson Rules that are relevant for your machine attribute:
- Nelson Rule 1: One point is more than three standard deviations from the mean.
- Nelson Rule 2: Nine, or more, points in a row are on the same side of the mean.
- Nelson Rule 3: Six, or more, points in a row are continuously increasing or decreasing.
- Nelson Rule 4: Fourteen or more points in a row alternate in direction, increasing then decreasing.
- Nelson Rule 5: Two or three points in a row are more than two standard deviations from the mean in the same direction.
- Nelson Rule 6: Four, or five, out of five points in a row are more than one standard deviation from the mean in the same direction.
- Nelson Rule 7: Fifteen points in a row are all within one standard deviation of the mean on either side of the mean.
- Nelson Rule 8: Eight points in a row exist, but none within one standard deviation of the mean, and the points are in both directions from the mean.
Trends are available in the corresponding machine view of the machine attribute.
In the Floor Plan view, or in the Production view for a factory, click the icon for the machine you want to monitor. Then select the Trends tab to look at the machine attribute trends.
Define a Trend
You need to define a trend before the trend model can be created for the machine attribute that you wish to monitor.
- Click Menu and select Configuration.
- Click the Trends tab.
- Click Add .
- Enter a name for the trend in the Name field.
- (Optional) Specify an optional description text for the trend.
- Under Data Analysis, select the Machine Type.
- Select the corresponding machine Attribute to monitor.
- Select a value for Detection:
- Automatic: Automatically chooses trends corresponding to all available Nelson Rules.
- Select Specific Trends: Lets you select one or more individual Nelson Rules that are relevant for your machine attribute.
- If you chose Select Specific Trends in the previous step, then select one or more Nelson Rules for your Trends.The description and graphical depiction of each rule are shown for you.
- Click Save to save the trend.You may need to Publish the trend if prompted. The system now starts building a trend model for the new trend. Trends are shown in the machine view after the trend model is ready.