Configure common historical attributes

Each application or system object that you select from the Template folder include a set of common attributes you configure to save data to the Historian. These are configured after activating the History feature in the Attributes page.

The historical attributes you configure are based on the data type of the object. For example, the following figure shows the common historical attributes for numerical attributes (integer, float, or double).

If you are configuring a boolean or string attribute, you see a smaller set of historical attributes. Similarly, a discrete field attribute will also have this same, smaller set of historical attributes.

This section describes the common historical attributes that you can configure for your system and application objects. Refer to this section as you complete the procedures to configure your objects.

• Force Storage Period

  Interval in milliseconds in which an attribute value is saved to the Historian, regardless of whether the value exceeds its value deadband setting or not. An attribute value is saved to the Historian at every Force Storage interval. The default value of zero (0) disables the Force Storage period.

• Value Deadband

  Threshold value in engineering units, which is the absolute difference between the current and most recent saved historical values. The current value must exceed the absolute deadband to be saved as historical data.

  The Value Deadband filters out small, momentary value changes from being saved to the Historian. A new value that is within the range of the deadband is not saved to the Historian. The default value of 0.0 disables the Value Deadband and any change to a value is saved as historical data.

• Trend Hi

  Initial maximum trend value in engineering units for clients. The default is 100.

• Trend Lo

  Initial minimum trend value in engineering units for clients. The default is 0.0.

• Enable Swinging Door

  A flag that indicates whether the swinging door rate deadband is enabled or disabled. The default is disabled.

  Enable Swinging Door is disabled if the historical attribute data type is Boolean or a string.

• Interpolation Type

  List of methods used by the Historian to interpolate analog historical data. The interpolation type determines which analog value is selected during a Historian data retrieval cycle. Interpolation types include System Default, Stairstep, or Linear. The default interpolation type is System Default.

  • Stairstep

    No interpolation occurs. The last known value is returned with the given cycle time. If no valid value can be found, a NULL is returned to the Historian.

  • Linear

    The Historian calculates a new value at the given cycle time by interpolating between the last known value prior to the cycle time and the first value after the cycle time.

  • System Default

    The Historian system-wide interpolation setting. The system-wide setting must be either stairstep or linear interpolated.

• Rollover Value

  Positive integer value that represents a tag’s reset limit when the Historian operates in counter retrieval mode. In counter retrieval mode the Historian uses a tag's rollover value to calculate and return the delta change between consecutive retrieval cycles. The default value is 0.0.

  The Rollover value applies only to numeric attributes. The Rollover value is disabled if the historical attribute data type is Boolean or a string.

• Rate Deadband

  Percentage rate of change deadband based on the change in the slope of incoming data values to the Historian. For example, specifying a swinging door rate deadband of 10 percent means that data is saved to the Historian if the percentage change in slope of consecutive data values exceeds 10 percent.

  The default is 0.0, which indicates a swinging door rate deadband is not applied. Any percentage greater than 0.0 can be assigned to the rate deadband.