Variable Property Definitions
There are many properties that need to be set for a variable to function. Variable properties are set in the Variable Sheet. The Variable Sheet can be obtained at any level of the plant model by right-clicking on any of the objects within the plant model.
Security Group
Security setting, which allows viewing, configuration and placement into any display. No Security Group is the default setting. Variable security can be set at the display-level to override variable-level security. Do this by setting the UseDisplaySecurity site parameter to True. Refer to "Display-Level Variable Security" in User-Defined Security Groups.
Data Source Write Group
This property is populated with user-defined data sources (data sources with an ID > 50000). If a data source is selected from the list, the Proficy Writer service will not write variable data to the historian tag defined in the Output Tag field or any specification data to any of the specification tag fields. This will enable you to perform tag reads and writes at a group level using the Proficy Plant Applications SDK. Please see the SDK chapter in the online help for more information on GroupSetup, GroupRead, and GroupWrite.
Data Source
Sets the variables source of data.
AutoLog manually entered data from an AutoLog worksheet.
CalculationMgr is a data source that allows a variable to be calculated from eight other variables and any number of constants.
Enterprise Connector
Historian uses Historians as the data source and allows Plant Applications variables to be used as the data source. The Historian variable, sampling type, and sampling interval properties must also be configured.
Other
SAP
Undefined default data source
Data Quality Comparison Type
It is the method of comparing the data quality comparison value to the data quality tag.
Equal To: If the value of the data quality tag equals the data quality comparison value, then ignore the value of the input tag.
Less Than: If the value of the data quality tag is less than the data quality comparison value, then ignore the value of the input tag.
Less/Equal To: If the value of the data quality tag is less than or equal to the data quality comparison value, then ignore the value of the input tag.
Greater Than: If the value of the data quality tag is greater than the data quality comparison value, then ignore the value of the input tag.
Greater/Equal To: If the value of the data quality tag greater than or equal to the data quality comparison value, then ignore the value of the input tag.
Not Equal To: If the value of the data quality tag is not equal to the data quality comparison value, then ignore the value of the input tag.
Data Quality Comparison Value
This is the value to be compared to the value of the data quality tag using the data quality comparison type. The value you enter in this field is assumed to be "bad."
Event Type
Defines the trigger to collect the data for the variable. Time is default setting. The available event types are determined by the events configured on the production unit with which the variable is associated.
Downtime: Fired on completion of a Downtime event and assigns the Downtime event period as the basic sampling window.
Export is used to trigger a file transfer to an external source
Genealogy a method to update a genealogy event status
Import is used to trigger a file transfer to Plant Applications
Product Change is used to trigger calculations and data collection based upon a product (grade) change.
Production Event a discrete event trigger by completion of a Batch, Package, Pallet, Reel, Roll or Set.
Schedule Change is used to trigger calculations and data collection based upon a schedule change (i.e. making a new process order active).
Time triggers data collection for a variable by a certain time frame defined by the properties Sampling Interval, Sampling Offset, and Sampling Window. Default setting.
UserDefined Event optional type for user-defined events
Waste is used to support additional events associated with the Waste and Downtime application module.
Event Sub Type
The Event Sub Type property contains the event subtype based on the event type (Production or User-defined) selected in the Event Type property.
Event Dimension
The Event Dimension property provides a list of event dimensions from which to select. For more information on production event dimensions, see the topic Planning Event Detection Models Or Time Tracking.
Engineering Units
Labels the variable's actual units for example gallons per minute (gpm), inches (in), feet per minute (fpm). These are only display labels and not for calculations.
Data Type
The Data Type for the variable defines what data can be entered in associated variable cells. The system has pre-configured data types, however you can also create custom data types. The system configured valid data types are:
Array Float an array of floating-point numbers between -9999999.999999 and 9999999.999999.
Array Integer an array of integer numbers between -36,768 and 36,768.
Array String an array of sequences of up to 25 characters.
Comment a comment variable (use when more than 25 characters are required).
Float a floating-point number.
Integer an integer number between 36,768 and 36,768.
Logical provides a checkbox in the AutoLog sheet for a variable.
String a sequence of characters (Limited to 25 characters or less. For longer strings, use Comment variables).
Custom Data Types are user defined pick lists that can be created and used for selecting multiple values for an AutoLog variable.
Precision
An integer that determines how many digits are displayed after the decimal point for floating point data types.
Repeating Value
Selecting this property will cause a variable's value to automatically repeat when a new column is added in an AutoLog display. When a new column is automatically added (determined by the Time Interval setting), the current value (including NULL) of the variable is automatically entered in the new column. Repeating is controlled by the following variable properties.
Repeating Maximum Window: optional
Sampling Interval: Sampling Interval must be greater than 1 for repeating to occur.
Data Source: The data source must be AutoLog, Enterprise Connector, Other, or SAP for Repeating Value to be able to be selected.
Repeating Maximum Window (Minutes)
When Repeating Value is selected, the number of minutes entered in the Repeating Maximum Window property determines how far back in time from the current time a repeating value can be changed in an AutoLog display, and have all the repeated values following the changed value also change. Changing a value outside the repeating maximum window will affect only the changed value.
NOTE: Values that are manually entered are never changed.
1 Value was changed from 9.00 to 9.35. All repeated values were also changed.
2 Value (9.55) was not changed because it was manually entered.
3 Cells are empty because there is no value at the time the column is added. For the variable, Samp Int 2, the value is repeated every two minutes (sampling interval = 2 with no offset); therefore, cells added at odd-numbered minutes (for example 9:25) are empty because there is no value in the Tests table at 9:25.
Should Archive
A variable can be set to show data to the Plant Applications Client applications but not be stored in the Plant Applications database. It can be used to temporarily turn off data collection and leave the configuration still intact. This check box is defaulted to True.
Default Test Frequency (AutoLog)
This property is used to schedule tests in AutoLog for Event based variables by coloring the cell (white is the default for test entry) in the AutoLog worksheet where data should be entered. The Default level test frequency is the lowest level where a variables test frequency can be managed if test frequency has not been defined in a variable level specification or a central level specification. The value is set to an integer number such as a 1 for scheduling tests to occur in every Autolog column, 2 for every other Autolog column, a 3 for every third Autolog column, and so on. 0 is for discretionary input, which is the default.
Reset Test Frequency (Time Based)
This resets Test Frequency schedule after a product change for time-based variables.
Force Test Frequency Reschedule
Upon a reject value being entered in a test field, if this box is checked, test frequency will be disabled and every test is scheduled until a non-reject value occurs in the test field.
Sampling Interval (Minutes)
The Sampling Interval only applies if the Event Type property is set to time. The sampling interval determines when, starting from midnight, data is collected from the historian or from Autolog (depending on the Data Source property) and inserted in the Plant Applications database.
NOTE: Setting the Time Information Interval display option to <none> will override the Sampling Interval. See Creating Time-based Displays. When <none> is selected as the interval, no records are written to the Test table until a column and value are manually inserted in the display.
Sampling Offset (Minutes)
The amount of time from midnight the interval is to be offset before the variable is to be triggered and data collection is started. Sampling Offset cannot be greater than the Sampling Interval.
Sampling Window Types
This property allows the configuration of variables that will calculate a running value (min, max, total, avg., etc.) at specified intervals throughout the shift, day, or month. These settings currently are multi-production unit or plant wide. The configuration for a shift and day is done in the Global Settings site parameters tab. Some set up is required to configure the end of day hour, end of day minute, shift interval, and shift offset from 12:00 midnight.
Day to Date Day to Date variables allow the user to set up variables that will calculate a running value (min, max, total, avg., etc.) at a specified interval throughout a user defined day. It can be used with data sources from Historian variables.
Month to Date Month to Date variables allow a user to set up running calculations (min, max, total, avg., etc.) from the beginning to the end of the month. The source of data for month to date variables can be from Historian variables.
Sampling Window this sampling window type is used in combination with the Sampling Window time to set the outer time frame for a rolling calculation.
Shift to Date Shift to Date variables allows a user to set variables that calculate a running (min, max, total, avg., etc.) value at a specified interval throughout a user defined shift. It can be used with data sources from Historian variables.
Sampling Window (Minutes)
Is used to set the amount of data (within a time frame) used in a calculation. The Sampling Window sets the outer time frame in a rolling type calculation. The inner time frame in a rolling type calculation is the sample interval and sets how frequently the rolling calculation is to occur.
For example, if the Sampling Interval is set to 120 minutes, the Sampling Window is set to 1440 minutes, and the Sampling Type is set to Average, then a 1440-minute average will be calculated every 120 minutes (rolling average).
For time based variables with an Historian data source the sampling window is limited to a maximum of 86400 minutes (1440 minutes * 60 days). You will not be able to enter any value above this number for such variables. If you attempt to enter a number greater than 86400, the last digit will not be added. For example, if you attempt to enter 86401, the last digit will be rejected and the result will be 8640.
Sampling Types
This property sets the type of calculations or sampling that can be used for a variable. These are described below.
% in Reject%: of the values over the time interval or event interval that are inside the reject limits. The variable reject and unit reject features apply to this data as well as to run summaries. You'll need to specify an input tag as the raw data source and another tag (see Sampling Reference) as the specification source.
% in Warning%: of the values over the time interval or event interval that are inside the warning limits. The variable reject and unit reject features apply to this data as well as to run summaries. You'll need to specify an input tag as the raw data source and another tag (see Sampling Reference) as the specification source.
Average: The statistical average value, Avg = Sum (xi)/n, over the Sampling Window (Minutes). The average is calculated by averaging adjacent values, time weighting each average value based on the duration of the interval, and then summing the time-weighted averages. If there is no value at the start time, the value will be interpolated based on the value before the start time. If there is no value at the end time, the value will be interpolated based on the value immediately following the end time. In the following example, the first value is an interpolated value based on a raw value of 59 with a timestamp of 12:23:33. The interpolated value was calculated as follows:
(59 2) * (7/247) + 2 where:
59 = raw value closest to start time
2 = first raw value within the interval window
7 = number of seconds first raw value is from start time
247 = difference, in seconds, between timestamp of value 59 and timestamp of value 2 (12:27:40 12:23:33)
Column A is the timestamp of the raw historian value
Column B is the raw historian value
Column C is the average of the adjacent values
Column D is the time-weighted value based on the duration interval (1/120 seconds in this example)
NOTE: The first value in the example, 3.615385, is an interpolated value and not the actual raw historian valueBase TimeStamp Sampling Types: Used for processing time of event over multiple units where many units are used and multiple events do not have to be created. For example, track processing time of a serial number (event) over many units. Event is created on first production unit. Normally the same event would be created on each subsequent unit and related through genealogy. Base Timestamp sampling types capture processing time on subsequent units where new events are not required or too numerous.
Base TimeStamp Interpolated: Interpolated value with respect to sample end time.
Base TimeStamp Last Good Value: Last good value with respect to sample end time.
Base TimeStamp NextGoodValue: Next good value with respect to sample end time.
Closest Good Value:Retrieves a snapshot value that is closest in time to the specified snapshot time. If there is no data available over the Sampling Window (Minutes) then there is no value returned for that time. The data will be read from the Historian for variables with an event type of production event after the event summary lag time has elapsed. The user parameter EventSmryLagTime defines how long the Summary Manager (SummaryMgr) service should wait after an event occurs before processing, calculating, or acquiring data for the variables that are defined with an event type of production event on that unit. If the variable is time based, the lag time is based on the read lag time set for the individual variable. Closest Good Value will only go forward in time as far as data is available in the historian past the snapshot timestamp.
Count: The number of values available over the Sampling Window (Minutes). The variable reject and unit reject features apply to this data as well as to run summaries.
Cp: A capability indicator for a stable process. Cp measures the process capability ratio. You will need to specify an input tag as the raw data source and another tag (see Sampling Reference) as the specification source.
Cp Calculation:
For supporting calculations, see Supporting Calculations for Cp, Pp, Cpk, Ppk.
Upper and lower specification limits (USL, LSL) are stored in the database table Var_Specs for each variable. If only one specification limit is given, Cp is not calculated.
Cpk:Process capability index. The variable reject and unit reject features apply to this data as well as to run summaries. You will need to specify an input tag as the raw data source and another tag (see Sampling Reference) as the specification source.
Cpk Calculation:
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Cpu = USL XBarBar / (ProductSummarizationSigma * Estimated Sigma)
Cpl = XBarBar LSL / (ProductSummarizationSigma * Estimated Sigma)
For supporting calculations, see Supporting Calculations for Cp, Pp, Cpk, Ppk
ProductSummarizationSigma (PSS) is a customizable site parameter. It assigns a value that is used as a multiplier in Cpu, Cpl, Ppu, and Ppl calculations. If this parameter is not specified, the default is the industry standard of 3.0. For example, if the value is changed to 2, then rather than having 3σ as the divisor for the Cpu calculation, you would have a divisor of 2σ. To change the PSS value, access the Product Summarization Sigma site parameter in the Administrator application. For details on changing the site parameter value, see Product Summarization Sigma.
If USL is not provided, Cpk = Cpl.
If LSL is not provided, Cpk = Cpu.
If both USL and LSL are not provided, Cpk cannot be calculated.
Negative Cpk values are allowed.
Discrete Average: Calculates a time-weighted average based on the raw samples in the sampling window.
Discrete Total: Calculates a time-weighted total based on the raw samples in the sampling window.
Note: Plant Applications supports three sampling types for averages and totals: Normal, Discrete, and Raw. Normal and Discrete are both time weighted, but Discete requires at least one raw value during the sampling interval to produce a value. Raw is an average or total of the Historian archive values and is not time weighted.
Event TimeStamp: When you create a variable with this sampling type, Plant Applications monitors the input tag and when the value of the tag matches an existing event number on the production unit, the input tag's timestamp is stored in the variable.
First Good Value: Retrieves the first value of the data between the start time and end time of an event. In other words, it will retrieve the first value with a timestamp closest to the start time of the event.
Increase: Calculates the difference between the interpolated values that are collected for the sampling interval (or event interval) using the start time and end time of the interval. The calculation takes into account the fact that the reset value may have been reached multiple times over the time interval. This sampling type is used to calculate totals that use a Historian tag that has totalized counters or totalized integrators stored for it. These counters or integrators have a specific value they reset at. The configuration requires Increase Max RPM be set to 500 and Increase Reset Value be set to 10000. See Raw Increase.
Interpolated: Snapshot value interpolated between the two nearest data points found at the specified time. If there is no data available over the Sampling Window (Minutes) then there is no value returned for that time. The data will be read from the Historian for variables with an Event Type of Production Even after the Event Summary Lag Time has elapsed. The user parameter EventSmryLagTime defines how long the Summary Manager Service should wait after an event occurs before processing, calculating, or acquiring data for the variables that are defined with an Event Type of Production Event on that unit. If the variable is Time Based, the lag time is based on the Read Lag Time set for the individual variable.
Last Good Value: Retrieves a snapshot value that is closest in time to the specified snapshot time looking only backward in time from the snapshot time. If there is no data available over the Sampling Window (Minutes) then there is no value returned for that time. The data will be read from the Historian for variables with an Event Type of Production Even after the Event Summary Lag Time has elapsed. The system parameter EventSmryLagTime defines how long the Summary Manager Service should wait after an event occurs before processing, calculating, or acquiring data for the variables that are defined with an Event Type of Production Event on that unit. If the variable is Time Based, the lag time is based on the Read Lag Time set for the individual variable.
Maximum: Maximum value over the time interval or event interval. If there is no data over the Sampling Window (Minutes) then no value is returned for that time.
Maximum TimeStamp: Timestamp of maximum value in data set.
Minimum: Minimum value over the Sampling Window (Minutes). If there is no data over the Sampling Window (Minutes) then no value is returned for that time.
Minimum TimeStamp: Timestamp of minimum value in data set.
Next Good Value: Retrieves a snapshot value closest in time looking only forward in time to the specified snapshot time. If there is no data available over the Sampling Window (Minutes) then there is no value returned for that time. The data will be read from the Historian for variables with an Event Type of Production Even after the Event Summary Lag Time has elapsed. This Site Parameter EventSmryLagTime defines how long the Summary Manager Service should wait after an event occurs before processing, calculating, or acquiring data for the variables that are defined with an Event Type of Production Event on that unit. If the variable is Time Based, the lag time is based on the Read Lag Time set for the individual variable. Next Good Value will only go forward in time as far as data is available in the historian past the snapshot timestamp.
Pp: Used to summarize a system's performance in meeting upper and lower specification limits. You will need to specify an input tag as the raw data source and another tag (see Sampling Reference) as the specification source.
Pp Calculation:
For supporting calculations, see Supporting Calculations for Cp, Pp, Cpk, Ppk.
Upper and lower specification limits (USL, LSL) are stored in the database table Var_Specs for each variable. If only one specification limit is given, Pp is not calculated.
Ppk: An index of process performance that tells how well a system is meeting specifications. You will need to specify an input tag as the raw data source and another tag (see Sampling Reference) as the specification source.
PpK Calculation:
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Ppu = USL XBar / (ProductSummarizationSigma * Sigma)
Ppl = XBar LSL / (ProductSummarizationSigma * Sigma)
For supporting calculations, see Supporting Calculations for Cp, Pp, Cpk, Ppk
ProductSummarizationSigma (PSS) is a customizable site parameter. It assigns a value that is used as a multiplier in Cpu, Cpl, Ppu, and Ppl calculations. If this parameter is not specified, the default is the industry standard of 3.0. For example, if the value is changed to 2, then rather than having 3S as the divisor for the Ppu calculation, you would have a divisor of 2S. To change the PSS value, access the Product Summarization Sigma site parameter in the Administrator application. For details on changing the site parameter value, see Product Summarization Sigma.
If USL is not provided, Ppk = Ppl.
If LSL is not provided, Ppk = Ppu.
If both USL and LSL are not provided, Ppk cannot be calculated.
Negative Ppk values are allowed.
Raw Average: Average value of archived data set in Sampling Window
Raw Count: Number of values in archived data set within Sampling Window
Raw Increase: Raw Increase calculates the increase the same way as Increase. The difference is that Raw Increase ignores the Event Type and Sampling Window and will always calculate the increase every 15 seconds.
Raw Maximum: Maximum value in archived data set within Sampling Window
Raw Minimum: Minimum value in archived data set within Sampling Window
Raw Standard Deviation: Standard Deviation of archived data set within Sampling Window
Raw Total: Total of archived data set values within Sampling Window.
Raw Unique Count: Number of unique values in a Raw data set.
Raw Values: Returned data set only includes asynchronous (archived) values over Sampling Window. Data is not interpolated. Returned data set returns a value of NULL if there are no archived values in Sampling Window.
Standard Deviation:Standard deviation is calculated using values over the Sampling Window (Minutes).
s = Sqr [(Sum(xi ))2- (Sum(xi ))2
/n) 2/n-1]
Total:The total is calculated using values over Sampling Window (Minutes). The total is calculated using the average x the total number of minutes, adjusted by the totalization factor. For more information on calculating the average, see sampling type Average. For more information about totalization factor, see Totalization Factor.
NOTE: Bad samples are not considered for Total calculation.
Interpolated Total vs Weighted Total In Plant Applications
Plant Applications calculates total with following interpolation, which is highly sensitive to various time differences between data samples:
Example
An example of the issue describing how long running 0 impacts result:
(((Value + NextValue) / 2.0) * ((double) SegmentTime / (double) m_TotalTime))
2023-01-23 09:49:53 Value : 0
2023-01-23 09:49:53 NextValue : 12375
2023-01-23 09:49:53 *StartTime64 : 133141599500000000
2023-01-23 09:49:53 *EndTime64 : 133141623140000000
2023-01-23 09:49:53 SegmentTime : 23640000000
2023-01-23 09:49:53 m_GoodTime : 24960000000
2023-01-23 09:49:53 m_TotalTime : 26680000000
2023-01-23 09:49:53 m_Average : 5637.83
This example is demonstrating how 0 impacts total between following data samples:
{29-Nov-2022 02:45:50(29-Nov-2022 01:45:50 UTC)|Good|| 0.000},
{29-Nov-2022 03:25:14(29-Nov-2022 02:25:14 UTC)|Good|| 12375.000},
In this example, the Plant Applications total variable calculates Total results as: 4277
Read Lag Time (Seconds)
The Read Lag Time property specifies how long to wait after the scheduled time before processing time-based and event-based variables.
Reload Flag
When selected (checked), the Reload Flag property will cause test frequency changes to take affect when there is a grade change.
Row Modified
The Row Modified property is an information-only field that indicates whether one of the variable's properties has been changed and not saved. If Row Modified displays Yes, this indicates that one of the variable's properties has been changed, but not saved. No indicates that no changes have been made since the last time the variable was saved.
Production Unit
The Production Unit property is an information-only field that displays the production unit to which the variable belongs.
Production Line
The Production Line property is an information-only field that displays the production line to which the variable belongs.
Server
The Server property is an information-only field that displays the server to which the variable belongs.
Group Order
The Group Order property is an information-only field that indicates the position of the variable group on a production unit. For example, if a production unit has three variable groups in the following order: Group A, Group B, Group C, the group order would be:
Variable Group Name |
Group Order |
Group A |
1 |
Group B |
2 |
Group C |
3 |
If the groups were rearranged, the group order would not change as shown in the following example:
Variable Group Name |
Group Order |
Group B |
1 |
Group A |
2 |
Group C |
3 |
Variable
The Variable property contains the name of the variable. You can use this property to change the name of the variable.
NOTE: If you change the name of a variable that is on a display (Autolog, for example) that is open in the Plant Applications Client, you must close the display and re-open it to see your changes.
Variable Alias
The Variable Alias property contains the variable's alias. You can use this property to change the variable's alias. For more information on using variable aliases, see the topic Using Aliases.
Variable Group
The Variable Group property is an information-only field that displays the variable group to which the variable belongs.
Variable Order
The Variable Order property is an information-only field that displays the position of the variable within the variable group.
SPC Calculation Type
The SPC Calculation Type property is an information-only field that displays the type of SPC calculation. For more information, see the topic Creating SPC Calculations.
SPC Variable Type
The SPC Variable Type property is an information-only field that displays the variable type for the parent and child variables.
String Specification Setting
The String Specification Setting property must be used with phrase (or string-based) alarms. The options determine which variables are available when configuring an alarm template. (For more information on configuring alarms, see the topic Configuring Alarms.) The following three options are available:
Equal Spec (Default)
When planning an Alarm Template to trigger from a numeric value, you must choose “Equal Specs (Default)" as the “String Specification setting” in the Variable Sheet. When numeric data types are used (for example, Float, Int, etc.), specification alarms can be used to trigger off the Target, Upper Reject, Upper Warning, or other alarm settings. In this mode, the specification defines the alarm condition. When the value of the variable matches the specification, an alarm is triggered.
Not Equal Spec
When planning an Alarm Templates to trigger from a "String" Data Type, you must choose "Not Equal Spec" as the “String Specification Setting” in the Variables Sheet. String data types can be triggered off only the Target specification. The logic to determine if an alarm should be triggered is as follows: 1) An alarm is not triggered if the test result is equal (=) to the target specification. 2) An alarm is triggered if the test result if lesser or greater than (< >) the target spec. This setting is required to correctly evaluate String values in Alarm Templates.
Use Phrase Order
An alarm event will trigger if the variable value is equal to the value of the phrase order. For example, For more information, see the topic, Using String Values for Alarms.
Also refer to Using String Values for Alarms.
Sampling Window Examples
To further illustrate the concepts in sampling types and intervals, consider the following examples:
Shift To Date Variables: Shift to Date variables allows the user to set up variables that will calculate a running (min, max, total, avg., etc) value at a specified interval throughout a user-defined shift.
Month To Date Variables: Month to Date variables allow the user to set up running calculations (min, max, total, avg., etc.) from the beginning to the end of a month.
Totalization Factor
Is a multiplying factor that allows variables to be expressed as equivalent units. The factor normalizes the units to a unit of a day. As an example, if the units for a variable are set to gal. per minute then the Totalization factor would be 1440 to convert minutes to a unit of a day.
Increase Max RPM
The Increase Max RPM parameter is the maximum rate per minute allowed. If this value is exceeded by consecutive data points, then those points are not used in the Increase calculation. Maximum practical rate increase for historian totalizer. Returns NULL if exceeded.
Increase Reset Value
Used to define historian point reset value. Increase Reset Value is the value at which the counter or totalizer is reset. This is used by the Increase and Raw Increase sampling types to determine what the increase was over the sampling window (or 15-second interval if Raw Increase is used). If Increase Reset Value is set to 0 (zero), the archived value is used as the reset value, if there is a decrease from the previous value to the current value.
Output Tag
Historian tag entered to be used to send data to Historian.
Input Tag
Historian tag entered to be used to retrieve data from Historian.
Input Tag 2
Historian tag entered to be used to retrieve data from Historian for the Event Timestamp sampling type.
Sampling Reference
The specification source for variables of sampling type % in Warning, % in Reject, Cpk, Cp, Ppk, and Pp. Sampling Reference is the tag that contains the specifications for the variable used for the Input Tag. These sampling types require raw data, along with specifications to compare the data against. Sampling Reference provides the specifications for the calculation and Input Tag retrieves the data.
Data Quality Tag
Historian tag is used in determining whether the data is of good quality or bad quality. The data quality tag is used with data quality comparison type and data quality comparison value to determine if the data is valid. Using data quality with certain sampling types may be affected by the data type of the data quality tag in the historian. If the data type is float, Plant Applications will interpolate, but if the data type is integer, Plant Applications will not interpolate.
Upper Entry Tag
Upper entry specification data is written to the historian tag in this field when a grade change event occurs.
Upper Reject Tag
Historian tag can be entered and used to send upper reject specification data to Historian when a grade change event occurs.
Upper Warning Tag
Historian tag can be entered and used to send upper warning specification data to Historian when a grade change event occurs.
Upper User Tag
Historian tag can be entered and used to send upper user specification data to Historian when a grade change event occurs.
Target Tag
Historian tag can be entered and used to send target specification data to Historian when a grade change event occurs.
Lower User Tag
Historian tag can be entered and used to send lower user specification data to Historian when a grade change event occurs.
Lower Warning Tag
Historian tag can be entered and used to send lower warning specification data to Historian when a grade change event occurs.
Lower Reject Tag
Historian tag can be entered and used to lower reject specification data to Historian when a grade change event occurs.
Lower Entry Tag
Historian tag can be entered and used to send lower entry specification data to Historian when a grade change event occurs.
Parent Variable
This property is a field that is defined if the variable being configured is a child variable. The child variable inherits the parent variables specifications and most of its properties.
Specification Property
It is the Property from where the Specification Variable originates.
Specification Variable
The Specification Variable that can be applied to the variable.
Specification Activation
This drop-down list defines when specifications will become active for this variable.
Product ChangeSpecification changes activated at the next product change after the approved transaction time.
ImmediateSpecification changes activated immediately at the time of the approved transaction time.
Variable Reject
This property is a check box that will cause the variable to become a variable reject variable.
If the variable's value falls outside of the set reject range during a grade run (set in the specifications for the variable), it will cause the data for the variable to be rejected for Run Summary calculations for the time period that the variable remains outside of the reject limits. Data for just this variable will be considered bad and will be rejected.
This property combined with the Unit Reject property will allow for segmentation of good data both for specific variables and for all variables on a production unit based on grade specifications.
Unit Reject
This property is a check box that will cause the variable to become a unit reject variable.
If a variables data value falls outside of the set reject range for a grade run (set as a specification for the variable), it will cause the variable data on the Production Unit to be rejected for the Run Summary. The Run summary will continue calculations for the variables time while it remains outside of the reject limit. Data for all variables on the production unit will be considered bad and will e rejected.
The unit reject property combined with the variable reject property will allow for segmentation of good data both for specific variables and for all variables on a production unit based on grade specifications.
Unit Summarize
If the box is checked the Run Summary Calculations will be performed for this variable at the end of each grade run. Checked is default.
Conformance Variable
Select this property if you want to track conformance for this variable. If all values are within target, conformance is "good." If at least one value is within the warning limits, conformance is "warning." If at least one value is within reject limits, conformance is "reject." By default, this property is selected.
Cpk Subgroup Size
The Cpk Subgroup Size property applies only if the selected Sampling Type is Cpk. Subgroup size is also known as the sample size.
Rank
This property allows weights to be set for variables according to their impact on the performance of the Production Unit and is used in calculating the Conformance Index.
Esignature Level
The Esignature Level property enables you to specify the level of approval that must be used to approve changes to the variable in the display. For more information on using e-signatures, see the chapter Using Electronic Signatures in the table of contents.
Extended Information
Used for providing information to interfaces or stored procedures.
User Defined 1-3
Can be used for any purpose suited for a variable, e.g. additional grouping of variables.
Force Signed Entry (+/-)
Autolog forces the operator to enter a (+) or (-) in front of data entry.
Test Variable Name
The Test Variable Name is the name of the variable to which this variable will be attached when the Data Source is set to Aliased.
Save Array Data
If one of the Array Data Types is selected, and this box is checked, the Array Data will be saved in the Plant Applications Database.
Perform Event Lookup
This affects only Production Event variables. If Perform Event Lookup is selected, an event must exist at the result_on time of the test value before the test value will be written to the database. By default, this option will be selected (it will be a 1 in the Variables table) for new variables. On an upgrade from versions prior to 5.0, Perform Event Lookup will not be selected (it will be a zero in the Variables table). If the Sampling Type is Raw Values, then Perform Event Lookup will always be set to zero (0).
Ignore Event Status
Turn on the flag to collect data when History Based on Event Status is selected as the value for the Populate Event_Detail_History, Populate Event_History, and Populate Waste_Event_Detail_History site parameters or the History Based On Event Status and Value Change for the Populate Test_History site parameter. Refer to Periodic Event Dimension Update.
Supporting Calculations for Cp, Pp, Cpk, Ppk
See also Weighted Sigma Calculations and Estimation of Sigma.
= Mean Range (Average of subgroup Ranges).
= Mean Moving Range of length 2 (Average of Ranges
taken with moving length of 2).
= Mean XBar (Average of subgroup Means).
In case of subgroup size = 1, this is the mean of all individual data.
= Mean Moving Range of length w
(Average of Ranges taken with moving length of w
).
is the sample standard deviation
= mean of all the observations; i.e., 
xi = individual observations
n = the total number of observations
m = the subgroup size in case of uniform subgroup size
d2, C4, d2(2) = SPC table constants (d2, C4 etc.) are retrieved for corresponding subgroup size if not specified otherwise (for example d2(2) is d2 for subgroup size 2).
where
Si = the ith subgroup Sigma
mi = the ith subgroup size and n is number of subgroups
When there is no variation in the data, standard deviation is zero, and therefore the resulting calculation will be NULL.
Weighted Sigma Calculations
For non-uniform subgroups the estimated sigma will be "weighted" as follows:
Estimation of Sigma
Sigma estimation is an automated process in Plant Applications. The following table outlines the method that is used.
Subgroup Size |
Number of Subgroups |
Run Sizes |
Sigma Estimation Method |
5 |
15 |
5 |
|
5 |
16 |
5 |
|
5 |
14 |
5 |
|
5 |
6 |
5 |
|
30 |
90 |
30 |
|
30 |
91 |
30 |
|
30 |
71 |
30 |
|
30 |
31 |
30 |
|
1 |
3 |
1 |
|