Access a Tag
About this task
- Access all the tags in all the systems available in the Historian server.
- Access the tags added to a specific collector instance.
- Access the tags added to all the collector instances in a specific Historian system.
MaxTagsToRetrieve
registry key under
HKEY_LOCAL_MACHINE\SOFTWARE\Intellution,
Inc.\iHistorian\Services\DataArchiver\, and then set the maximum
number of tags that you want to retrieve. Restart the Historian Data Archiver
service for the change to reflect.Procedure
- Access Configuration Hub.
-
In the NAVIGATION section, under the Configuration Hub
plugin for Historian, select Tags.
A list of all the tags appears, displaying the following information.
Column Description TAG NAME The name of the tag. DESCRIPTION The description of the tag. COLLECTOR NAME The name of the collector instance to which you have added the tag. LAST 10 VALUES The last 10 values collected for the tag, plotted as a trend chart. If you pause over the chart, the minimum, maximum, first, and last values among the 10 values appear. TAG ALIAS Indicates whether the tag contains aliases, which are created when you rename the tag using an alias. Tip: You can show/hide/reorder columns in the table. For instructions, refer to Common Tasks in Configuration Hub. -
If you want to access the tags specific to a Historian system, in the drop-down
list box in the upper-left corner of the main section, select the system.
Alternatively, you can access the system from the NAVIGATION section, right-click the system (or select
), and then select Browse Tags.
The list of tags is filtered to display only the tags specific to the system. -
If you want to narrow down the search results, select
Search.
Enter the search criteria, and then select Search. You can add more attributes by selecting Add Attribute. You can enter a name or a value partially or use the wildcard character asterisk (*).
The tags are filtered based on the search criteria. -
Select the row containing the tag that you want to access.
The tag details appear in the DETAILS section.
Table 1. The General Section Field Description Tag Name The name of the tag. This field is disabled and populated. Description The description of the tag. Comment Comments that apply to the tag. StepValue Indicates that the actual measured value changes in a sharp step instead of a smooth linear interpolation. This option is applicable only for numeric data. Enabling this option only affects data retrieval; it has no effect on data collection or storage. Last Modified Time The date the last tag parameter modification was made. This field is disabled and populated. Last Modified User The name of the person who last modified the tag configuration parameters. This field is disabled and populated. Table 2. The Collection Section Field Description Collector The name of the collector that collects data for the selected tag. Source Address The address for the tag in the data source. Leave this field blank for tags associated with the Calculation or Server-to-Server collector. For Python Expression tags, this field contains the full applicable JSON configuration, which includes an indication of the source address.
Note: When exporting or importing tags using the Excel Add-in for Historian, the Calculation column, not the SourceAddress column, holds the formulas for tags associated with the Calculation or Server-to-Server collector.Data Type The data type of the tag. 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.
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.Value The number of bytes for a fixed string data type. This field is enabled only for fixed string data types. Enumerated Set Name The name of the enumerated set that you want to assign to the tag. Array Tag Indicates that the tag is an array tag. Location The distributed location of the system in which the tag data is stored (applicable only for a horizontally scalable system). Data Store The data store in which the tag data is stored. Collection Indicates whether data collection is enabled or disabled for the tag. If you disable collection for the tag, Historian stops collecting data for the tag, but does not delete the tag or its data. Collection Type 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 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. Similarly, 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 The precision for timestamps, which can be either seconds, milliseconds or microseconds. Condition-Based Indicates whether condition-based data collection is enabled. Trigger Tag The name of the trigger tag used in the condition. Comparison The comparison operator that you want to use in the condition. Select one of the following options: - 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 A target value that you want to compare with the value of the trigger tag. If using = and != comparison parameters, ensure 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 Indicates whether end-of-collection markers are 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. Table 3. The Collection Options Section Field Description Data Collection Indicates whether data collection is enabled or disabled for the tag. If you disable collection for the tag, Historian stops collecting data for the tag, but does not delete the tag or its data. Collection Type The type of data collection used for this tag: - Polled: The data collector requests data from the data source at the collection interval specified in the polling schedule.
- Unsolicited: The data source sends data to the collector whenever necessary (independent of the data collector polling schedule).
Collection Interval The time interval between readings of data from this tag. For unsolicited collection type, this field defines the minimum interval at which unsolicited data should be sent by the data source. Collection Offset Value and 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. Similarly, 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 The precision for timestamps, which can be either seconds, milliseconds or microseconds. Condition based collection Indicates whether condition-based data collection is enabled. Trigger Tag The name of the trigger tag used in the condition. Comparison The comparison operator that you want to use in the condition. This field is enabled only if you have enabled condition-based collection. Select one of the following options: - 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 A target value that you want to compare with the value of the trigger tag. If using = and != comparison parameters, ensure 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 Indicates whether end-of-collection markers are 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. Table 4. The Scaling Section Field Description EGU Description The Engineering Units (EGU) provide context to a tag's value by providing an accurate representation of the tag values through their corresponding units. This will help you to know the units of data that you pull. For example, you can enter "Temperature" or "degree Celsius" in EGU Description for a single tag or multiple tags associated with temperature values.
When you view the last 10 values of the tag, or when you generate a query/write report in the Data page, EGU you enter will be displayed under the Engineering Units column in the table view and as a tool tip in the trend view.
Hi Engineering Units The current value of the upper 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. However, not all OPC Servers make this information available. 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.
Lo Engineering Units The current value of the lower range limit of the span for this tag. Input Scaling Indicates whether input scaling is enabled, 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, 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, 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, Historian records a bad data quality for the data point.
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:- Hi Engineering Units: Enter 0.
- Lo Engineering Units: Enter 1.
- Hi Scaling Value: Enter 0.
- Lo Scaling Value: Enter -1.
- Input Scaling: Enable this option.
Hi Scaling Value The upper limit of the span of the input value. Lo Scaling Value The lower limit of the span of the input value. Table 5. The Collector Compression Section Field Description Collector Compression Indicates whether collector compression is enabled. Collector Deadband and Deadband value 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:
Suppose the engineering units are 0 to 200. Suppose 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 case, 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. For information, refer to Enable Spike Logic.
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. This 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 percentage and Historian converts the percentage in to engineering units.
Compression Timeout and Compression Timeout Interval Indicates the maximum amount of time the collector will wait between sending samples for a tag to the archiver. This time is maintained per tag, as different tags report to the archiver at different times. For polled tags, this 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 is logged on each compression timeout. For example, an unsolicited tag with a 1-second collection interval and a 30-second compression timeout is 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 6. The Archive Compression Section Field Description Archive Compression Indicates whether archive compression is enabled. If enabled, Historian applies the archive deadband settings against all reported data from the collector. Archive Deadband and Deadband value The current value of the archive deadband, expressed as a percent of span or an absolute number. 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. Compression Timeout and Compression Timeout Interval 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.
Table 7. The Advanced Section Field Description Time Assigned By The source of the timestamp for a data value is either the collector or the data source. 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 is not changing.
However, if you set 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.
Note: This field is disabled for Calculation and Server-to-Server tags.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 field 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: This field only applies to tags associated with the Server-to-Server collector that use a polled collection type.Table 8. The Security Section Field Description Read Group The Windows security group that can retrieve the tag data and plot it in a trend chart. For example, if you select a group with power users, in addition to members of the iH Security Admins group, only a member of the power users group will be able to read data for that tag. Even a member of the iH Readers group will not be able to access data for that tag, unless they are also defined as a member of the power users group.
Write Group The Windows security group that can write tag data (for example, using the Excel Add-in for Historian). Administer Group The Windows security group that can create, modify, and delete the tag. For more information, refer to implementing tag-level security.
Note: When it comes to the group security, the security settings applied at the tag level, if any, take the precedence over those at the data store level.Note: If you are using domain groups (instead of local groups), the Read Group, Write Group, and Administer Group fields contain only the groups whose names begin with iH<space> (case-sensitive). Therefore, ensure that the group that you want to use begins with iH<space>.
For information on how these values are calculated, refer to Counter Delta Queries.Table 9. The Delta Query Section Field Description Delta Max Value The maximum value that a tag can have. It also called the rollover point of the counter or totalizer. If the tag values exceed MaxValue, the counter is reset to the minimum value. If you do not provide MaxValue, the delta query cannot check for a positive counter wrap. Delta Min Value The minimum value that a tag can have. If the tag values are less than MinValue (and the counter is going in the negative direction), the tag values are reset to MaxValue. If you do not provide MinValue, 0 is considered. Delta Max Positive RPH The maximum rate per hour between two consecutive data points in the positive direction. If two consecutive data points exceed this value, they are not considered in a delta query. Delta Max Negative RPH The maximum rate per hour between two consecutive data points in the negative direction. If two consecutive data points exceed this value, they are not considered in a delta query. The Delta Max Positive RPH and Delta Max Negative RPH values are used to determine if a counter wrap has occurred or if the counter has been manually reset. They help ignore data points whose values increase or decrease drastically.
The Spare Fields section
Spare configuration enables you to add additional configuration to the tag using the Spare Field 1 to Spare Field 5 fields in all the collectors except in a Server-to-Server collector, Server-to-Server distributor, and an OSI PI distributor.- In case of an OSI PI distributor, data is read from the Historian tag displayed in the Source Address field and sent to the OSI PI tag name displayed in the Spare Field 1 field. To control the source and destination tags, change the Source Address and Spare Field 1 values. You can add or update values in the remaining spare fields.
- In case of Server-to-Server collector and Server-to-Server distributor, you can update the Spare Field 1 to Spare Field 4 values, but the Spare Field 5 field is used only for internal purposes. Therefore, do not update the Spare Field 5 field.
The TAG ALIAS Section
Contains a list of the old names of the tag that you have renamed using an alias. For more information, refer to Rename a Tag.