Display and Edit Tag Parameters and Options

The fields in the right-hand column of the Tag Maintenance page allow you to view and edit specific tag parameters and options. To modify the values, enter new values in the appropriate fields and then select the Update button at the bottom of the page to apply the changes.
Action Buttons
All tabs in the Tag Maintenance page contain action buttons. Select a button to perform the action indicated by the name. If you want to cancel changes and return to the original values or settings, open a different page and then return to the Tag Maintenance page.
Button Description
Update Apply all parameter changes you have made on any tabs in this page.
Delete Delete the selected tag. You can either remove the tag from Historian or just stop collection of data from the tag by selecting the appropriate button and then selecting OK. This action deletes the tag, but does not delete any data for that tag.
The General Section
To display or edit general parameters listed below, select General. To modify the values, enter new values in the appropriate fields and then select the Update button at the bottom of the page to apply the changes. Until you select the Update button, entering a new value changes the display of the field name to blue.
Field Description
Description The tag description of the selected tag.
EGU Description The engineering units, if any, assigned to the selected tag.
Comment Comments, if any, that apply to the selected tag.
StepValue This tag property is used to indicate that the actual measured value changes in a sharp step instead of a smooth linear interpolation. This option should only be selected for numeric data. Enabling this option only affects data retrieval; it has no effect on data collection or storage.
Spare Configuration The Spare 1 through Spare 5 fields list any configuration information stored in these fields.
Note: Do not add or update the following spare configurations as the data may get corrupted or over written:
  • The Spare 1 field for OSI PI Distributor. OSI PI distributor reads data from the Historian tag displayed in the Tag Source Address field and sends it to the OSI PI tag name displayed in the Spare 1 field.
  • The Spare 5 field for Server to Server Collector and Server to Server Distributor as it is only used for internal purposes.
The Collection Section
To display or edit collection parameters, select Collection. The page shown in the following figure appears.

To modify the values, enter new values in the appropriate fields and then select the Update button at the bottom of the page to apply the changes. Until you select the Update button, entering a new value changes the display of the field name to blue.

The fields in the Collection section contain the following information:

Table 1. Data Source
Field Description
Collector The name of the collector for the selected tag. Select the drop-down arrow to display a list of all collectors.
Source Address

The address for the selected tag in the data source. Select the Browse button (...) to display a browse window.

Leave the Source Address field blank for Calculation and Server-to-Server tags.

For Python Expression tags, the Source Address field contains the full applicable JSON configuration, which includes an indication of the source address. The Browse button (…) is disabled for such tags.

Note: When exporting or importing tags using the EXCEL Add-In, the Calculation column, not the SourceAddress column, holds the formulas for the Calculation or Server-to-Server tags.
Data Type A list of data types.
Note: If you change the data type of an existing tag between a numeric and a string or binary data type (and vice versa), the tag's compression and scaling settings will be lost.
Enumerated Set Name The name of the Enumerated Set that can be assigned to the tags. Select the Browse button (...) to display the Define Enumerated Set window.
Data Length The number of bytes for a fixed string data type. This field is active only for fixed string data types. This field is adjacent to the Data Type field.
Is Array Tag Indicates the tag is an array tag.

Choosing a Data Type: The main use of the scaled data type is to save space, but this results in a loss of precision. Instead of using 4 bytes of data, it only uses 2 bytes by storing the data as a percentage of the EGU limit. Changing the EGU limits will result in a change in the values that are displayed. For example, if the original EGU values were 0 to 100 and a value of 20 was stored using the scaled data type and if the EGUs are changed to 0 to 200, the original value of 20 will be represented as 40.

Table 2. Collection Options
Field Description
Collection Select the appropriate option to enable or disable collection for this tag. The default setting is Enabled. If you disable collection for the tag, Historian stops collecting data for the tag, but does not delete the tag or any data.
Collection Type Select the type of data collection used for this tag, which can be polled or unsolicited. Polled means that the data collector requests data from the data source at the collection interval specified in the polling schedule. Unsolicited means that the data source sends data to the collector whenever necessary (independent of the data collector polling schedule).
Collection Interval Enter the time interval between readings of data from this tag. With Unsolicited Collection Type, this field defines the minimum interval at which unsolicited data should be sent by the data source.
Collection Offset Used with the collection interval to schedule collection of data from a tag. For example, to collect a value for a tag every hour at thirty minutes past the hour (12:30, 1:30, 2:30, and so on), enter a collection interval of 1 hour and an offset of 30 minutes. As another example, to collect a value each day at 8am, enter a collection interval of 1 day and an offset of 8 hours.
Note: If you enter a value in milliseconds, the value must be in intervals of 1000 ms. For example, 1000, 2000, and 3000 ms are valid values, but 500 and 1500 ms are invalid. The minimum value is 1000 ms.
Time Resolution Select the precision for timestamps, which can be either seconds, milliseconds or microseconds.

Condition based collection: Condition based collection is a method to control the storage of data for data tags by assigning a condition. Data is always collected but it is only written to the Data Archiver if the condition is true; otherwise, the collected data is discarded.

This condition is driven by a trigger tag; a tag collected by the collector evaluating the condition. Ideally, Condition based Collection should be used only with tags that are updating faster than the trigger tag. Condition based collection can be used to archive only the specific data which is required for analysis, rather than archiving data at all times, as the collector is running.

For example, if a collector has tags for multiple pieces of equipment, you can stop collection of tags for one piece of equipment during its maintenance. It is typically used on tags that use fast polled collection but you don't want to use collector compression. While the equipment is running, you want all the data but when the equipment is stopped, you don't want any data stored. The trigger tag would also typically use polled collection. But, either tag could use unsolicited collection.

The condition is evaluated every time data is collected for the data tag. When a data sample is collected, the condition is evaluated and data is either queued for sending to archiver, or discarded. If the condition cannot be evaluated as true or false, like if the trigger tag contains a bad data quality or the collector is not collecting the trigger tag, the condition is considered true and the data is queued for sending.

No specific processing occurs when the condition becomes true or false. If the condition becomes true, no sample is stored to the data tag using that condition, but the data tag will store a sample next time it collects. When the condition becomes false, no end of the collection marker is stored until the data tag is collected.

For example, if the condition becomes false at 1:15 and the data tag gets collected at 1:20, the end of collection marker will be created at 1:20 and have a timestamp of 1:20, not 1:15.

Condition based collection is supported by only archiver and collectors of Historian version 4.5 and above. Condition based collection does not apply to alarm collectors. This condition based collection is applicable to the following collectors only:
  • Simulation Collector
  • OPC Collector
  • iFIX collector
  • PI Collector
Table 3. Condition Based Collection
Field Description
Condition Based Select the appropriate option to enable or disable Condition Based Collection for a tag. The default setting is Disabled.
Trigger Tag The name of the tag used in the condition. Use the browse button to select a trigger tag from the list of tags associated with the collector.
Comparison Select the appropriate comparison operator from the drop-down list. Below is the list of comparison operator parameters:
  • Undefined: Collection will resume only when the value of the triggered tag changes. This is considered an incomplete configuration, so condition based collection is turned off and all the collected data is sent to archiver.
  • < =: Setting condition as Trigger Tag value less than or equal to the Compare Value.
  • > = Setting condition as Trigger Tag value greater than or equal to the Compare Value.
  • <: Setting condition as Trigger Tag value less than the Compare Value.
  • >: Setting condition as Trigger Tag value greater than the Compare Value.
  • =: Setting condition as Trigger Tag value equals Compare Value.
  • !=: Setting condition as Trigger Tag value not the same as Compare Value.
Compare Value Enter an appropriate target value to be compared against the value of the Trigger tag. Make sure when using '=' and '!=' comparison parameters that the format of the compared value and triggered tag are the same. For example, for a float type trigger tag, the compare value must be a float value; otherwise, the condition result is an invalid configuration. When the configuration is invalid, condition based collection is disabled and all data is sent to archiver.
End of Collection Markers Select the appropriate option to enable or disable End of Collection markers. The default setting is enabled. This will mark all the tag's values as "Bad", and sub-quality as "ConditionCollectionHalted" when the condition becomes false. Trending and reporting applications can use this information to indicate that the real world value was unknown after this time until the condition becomes true and a new sample is collected. If disabled, a bad data marker is not inserted when the condition becomes false.
The Scaling Section

Scaling converts a data value from a raw value expressed in an arbitrary range of units, such as a number of counts, to one in engineering units, such as gallons per minute or pounds per square inch. The scaled data type can serve as a third form of data compression, in addition to collector compression and archive compression, if it converts a data value from a data type that uses a large number of bytes to one that uses fewer bytes.

To display or edit scaling parameters, select Scaling. The page shown in the following figure appears.



To modify the values, enter new values in the appropriate fields and then select the Update button at the bottom of the page to apply the changes. Until you select the Update button, entering a new value changes the display of the field name to blue. The fields in the Scaling section contain the following information:
Table 4. Engineering Unit Range
Field Description
Hi Engineering Units Displays the current value of the upper range limit of the span for this tag.
Lo Engineering Units Displays the current value of the lower range limit of the span for this tag

Engineering Hi and Lo are retrieved automatically for F_CV fields for iFIX tags; all others are left at default settings. When adding tags from the server using an OPC Collector, the OPC Collector queries the server for the EGU units and EGU Hi/Lo limits. Not all OPC Servers make this information available, however. Therefore, if the server does not provide the limits when requested to do so, the collector automatically assigns an EGU range of 0 to 10,000.

Table 5. Input Scaling
Field Description
Input Scaling Select the appropriate option to enable or disable input scaling, which converts an input data point to an engineering units value.

For example, to rescale and save a 0 - 4096 input value to a scaled range of 0 - 100, you enter 0 and 4096 as the low and high input scale values and 0 and 100 as the low and high engineering units values, respectively.

If a data point exceeds the high or low end of the input scaling range, then Historian logs a bad data quality point with a ScaledOutOfRange subquality. In the previous example, if your input data is less than 0, or greater than 4096, then Historian records a bad data quality for the data point. For instance, a value of 4097, in this example, yields a bad data quality.

Hi Scale Value The upper limit of the span of the input value.
Lo Scale Value The lower limit of the span of the input value.
OPC Servers and TRUE Values: Some OPC Servers return a TRUE value as -1. If your OPC Server is returning TRUE values as -1, modify the following scaling settings in the Tag Maintenance page of Historian Administrator: 
Hi Engineering Units = 0
Lo Engineering Units = 1 
Hi Scale Value = 0 
Lo Scale Value = - 1 
Input Scaling = Enabled
The Compression Section
Note: Array tags do not support Archive and Collector Compression. If the tag is an array tag, then the Compression section is disabled.

To display or edit compression parameters, select Compression. The page shown in the following figure appears.



To modify the values, enter new values in the appropriate fields and then select the Update button at the bottom of the page to apply the changes. Until you select the Update button, entering a new value changes the display of the field name to blue. The fields in the Compression section contains the following information:

Table 6. Collector Compression
Field Description
Collector Compression (Enabled, Disabled) Select the appropriate option to enable or disable compression at the collector level.

Collector compression applies a smoothing filter to incoming data by ignoring incremental changes in values that fall within a deadband centered around the last reported value. The collector reports any new value that falls outside the deadband to the Historian archive and then centers the deadband around the new value.
Collector Deadband The current value of the compression deadband. This value can be computed as a percent of the span, centered around the data value or given as an absolute range around the data value.
Note: Some OPC Servers add and subtract the whole deadband value from the last data value. This effectively doubles the magnitude of the deadband compared to other OPC Servers. To determine how your specific server handles deadband, refer to the documentation of your OPC Server.

Example:

The engineering units are 0 to 200. The deadband value is 10%, which is 20 units. If the deadband value is 10% and the last reported value is 50, the value will be reported when the current value exceeds 50 + 10 = 60 or is less than 50 - 10 = 40. Note that the deadband (20 units) is split around the last data value (10 on either side.)

Alternatively, you could specify an absolute deadband of 5. In this instance, if the last value was 50, a new data sample will be reported when the current value exceeds 55 or drops below 45.

If compression is enabled and the deadband is set to zero, the collector ignores data values that do not change and records any that do change. If you set the deadband to a non-zero value, the collector records any value that lies outside the deadband. If the value changes drastically, a pre-spike point may be inserted. See Spike Logic for more details.

Engineering Unit Converts the deadband percentage into engineering units and displays the result. This value establishes the deadband range that is centered around the new value.

When enabling Archive Compression or Collector Compression, the Engineering Units field represents a calculated number created to give an idea of how large a deadband you are creating in Engineering Units. The deadband is entered in % and Historian multiplies that % by the range (Hi Engineering Units - Lo Engineering Units) to compute the % in Engineering Units.
Collector Compression Timeout Indicates the maximum amount of time the collector will wait between sending samples for a tag to the archiver. This time is kept per tag, as different tags report to the archiver at different times.

For polled tags, the Collector Compression Timeout value should be in multiples of your collection interval. After the timeout value is exceeded, the tag stores a value at the next scheduled collection interval, and not when the timeout occurred. For example, if you have a 10 second collection interval, a 1 minute compression timeout, and a collection that started at 2:14:00, if the value has not changed, the value is logged at 2:15:10 and not at 2:15:00.

For unsolicited tags, a value is guaranteed in, at most, twice the compression timeout interval.

A non-changing value would be logged on each compression timeout. For example, an unsolicited tag with a 1 second collection interval and a 30 second compression timeout would be stored every 30 seconds.

A changing value for the same tag may have up to 60 seconds between raw samples. In this case, if the value changes after 10 seconds, then that value is stored, but the value at 30 seconds (if unchanged) will not be stored. The value at 60 seconds will be stored. This leaves a gap of 50 seconds between raw samples which is less than 60 seconds.

Compression timeout is supported in all collectors except the PI collector.

Table 7. Archive Compression
Field Description
Archive Compression (Enabled, Disabled) Select the appropriate option to enable or disable compression at the Historian archive level. If enabled, Historian applies the archive deadband settings against all reported data from the collector.
Archive Deadband The current value of the archive deadband, expressed as a percent of span or an absolute number.

Each time the system reports a new value, it computes a line between this data point and the last archived value. The deadband is calculated as a tolerance centered about the slope of this line. When the next data point is reported, the line between the new point and the last archived point is tested to see if it falls within the deadband tolerance calculated for the previous point. If the new point passes the test, it is reported and is not archived. This process repeats with subsequent points. When a value fails the tolerance test, the last reported point is archived and the system computes a line between the new value and the newly archived point, and the process continues.

Engineering Unit Converts the deadband percentage into engineering units and displays the result. This value establishes the deadband range that is centered around the new value.

When enabling Archive Compression or Collector Compression, the Engineering Units field represents a calculated number created to give an idea of how large a deadband you are creating in Engineering Units. The deadband is entered in % and Historian multiplies that % by the range (Hi Engineering Units - Lo Engineering Units) to compute the % in Engineering Units.
Archive Compression Timeout Indicates the maximum amount of time from the last stored point before another point is stored, if the value does not exceed the archive compression deadband.

The data archiver treats the incoming sample after the timeout occurs as if it exceeded compression. It then stores the pending sample.
Calculation Tab
Note: The Calculation section applies only to Calculation and Server-to-Server tags. The Calculation section is disabled for array tags.

To display calculation parameters, select Calculation.

The page shown in the following figure appears.



To modify the calculation formula, enter new values in the appropriate fields and then select Update at the bottom of the page to apply the changes. Until you select the Update button, entering a new value changes the display of the field name to blue.

Calculation Pane

The Calculation pane is where you build your calculation formula. You can either type the VB Script directly or use the Insert Function Wizard. See Building Calculation Formulas Using the Wizard for more information. Calculation Triggers defines the appropriate trigger for all tags that have a Collection Type set to Unsolicited rather than Polled.

There are several buttons associated with the Calculation pane.
  • The Wizard, Tag, and Time buttons are associated with the Insert Function Wizard and allow you to use the wizard to directly populate syntax within the Calculation pane.
  • The Test button allows you to verify the syntax within your calculation formula.
  • Use the Clear button to clear the Calculation pane.
  • The Window button expands the Calculation pane.
The Advanced Section

To display or edit advanced parameters, select Advanced.

The page shown in the following figure appears.



To modify the values, enter new values in the appropriate fields and then select the Update button at the bottom of the page to apply the changes. Until you select the Update button, entering a new value changes the display of the field name to blue.

The fields in the Advanced section contain the following information:

Table 8. Data Collection Options
Field Description
Time Assigned By The source of the timestamp for a data value is either the collector or the data source.
Note: This field is disabled for Calculation and Server-to-Server tags.

All tags, by default, have their time assigned by the collector. When you configure a tag for a polled collection rate, the tag is updated based on the collection interval. For example, if you set the collection interval to 5 seconds with no compression, then the archive will be updated with a new data point and timestamp every 5 seconds, even if the value isn't changing.

However, if you change the Time Assigned By field to Source for the same tag, the archive only updates when the device timestamp changes. For example, if the poll time is still 5 seconds, but if the timestamp on the device does not change for 10 minutes, no new data will be added to the archive for 10 minutes.
Time Zone Bias The number of minutes from GMT that should be used to translate timestamps when retrieving data from this tag. For example, the time zone bias for Eastern Standard time is -300 minutes (GMT-5).

This property is not used during collection. Use this option if a particular tag requires a time zone adjustment during retrieval other than the client or server time zone. For example, you could retrieve data for two tags with different time zones by using the tag time zone selection in the iFIX chart.

Time Adjustment If the Server-to-Server Collector is not running on the source computer, select the Adjust for Source Time Difference option to compensate for the time difference between the source archiver computer and the collector computer.
Note: The Time Adjustment field only applies to Server-to-Server tags that use a polled collection type.
Data Store Displays the data store the tag belongs to.

Refer to Implementing Historian Security for definitions of the various security levels and groups.

Table 9. Security
Field Description
Read Group The Windows security group assigned to the selected tag. Refer to Implementing Historian Security for definitions of the various security levels and groups.
Write Group The Windows security group assigned to the selected tag.
Administer Group The Windows security group assigned to the selected tag.
Table 10. Audit
Field Description
Last Modified The date the last tag parameter modification was made.
Modified By The name of the person who last modified the tag configuration parameters.