Limits Overview

Setting field limits will set the qualities of all tag values that exceed either the HighHigh or the LowLow limits to bad. All bad quality data points will not be used during model construction and only good quality data, in other words, data that falls within the HighHigh and LowLow limits, will be used for modeling purposes.

The Continuous Troubleshooter assigns limits automatically to each variable when importing the data file. The simplest way to re-define these limits for any variable is to simply enter the appropriate limits in the tabular Data Cleaning View. The user can enter value for the LowLow, Low, HighHigh and High limits manually.

However, most users would want to inspect their data visually before editing the limits in the Data Cleaning View. For this reason, Troubleshooter provides the user with quick access to two data analysis tools from the Data Cleaning View, the Histogram and time-series Trend Tools.

There are four limits that can be configured for each variable:

Low Low

The Lowlow limit is the absolute (engineering) minimum value that a model variable may have. A typical use of the LowLow limit is to set the data quality of all values that are less than the LowLow limit to "bad quality". All "bad quality" data will not be used in model construction.
Low

The Low limit is a secondary limit that indicates the "operational" lower limit of a variable. By default, the low limit is set to 1 standard deviation from the mean.
High

The High limit is a secondary limit that indicates the "operational" higher limit of a variable. By default, the high limit is set to 1 standard deviation from the mean.
High High

The HighHigh limit is the absolute (engineering) maximum value that a model variable may have. A typical use of the HighHigh limit is to set the data quality of all values that are less than the HighHigh limit to "bad quality". All "bad quality" data will not be used in model construction.

NOTE: The High and Low limits configured are used in constructing the rule-based process model. Be sure to set the High and Low limits to the desired or "normal" limits for the process target.