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
CollectorThe 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 NameThe 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
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 IntervalEnter 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
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.
ComparisonSelect 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 ValueEnter 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 MarkersSelect 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.