Value duration (BValueDurationBlock)
A trend request results in values that reflect the duration of the current value within the trend. A trend request typically yields a sawtooth output, where the accumulated duration value resets to zero and each value in the trend data changes.
For a value request, the Search Limit property (defaults to 1 hour) defines the time range for the block to process a trend request and returns a single value
that reflects the duration of the current value in the trend.
Figure 174. Value Duration properties
To view these properties, double-click the block on the Wire Sheet or the block name in the Nav tree.
| Property | Value | Description |
|---|---|---|
| Out | read-only value slot | Outputs a constant value of constant trend from the Trend In property based on the value of the Make Trends or Makes Trends property.
|
| Trend In | required value slot | Links from the output of other logic blocks or data sources to supply trend data to the current logic block. |
| Mode | drop-down list defaults to Minutes (defaults to 1 hour)
|
Configures what time unit (milliseconds, seconds, minutes or hours) to apply to the accumulated values. |
| Search Limit | hours minutes seconds miliseconds (defaults to 1 hour) | Defines how far back in time to search. The system subtracts this value from the current time to create a time range for value requests. |
| Makes Trends | true or false (default)
|
Controls the processing of trend requests.
|
Example
For a value request, the Search Limit property (defaults to 1 hour) defines the time range of data to query and the Mode property (defaults to Minutes) defines the time interval for the result. Consider an algorithm with a Value Duration Block configured with Mode = Hours and Search Limit = 24 hours.
Figure 175. Value Duration Block algorithm
The history for the hs:power data source shows the value has been 300 since 9:00 AM.
Figure 176. Resulting data
A Numeric Point for an analytic proxy extension configured with Data = alg:ValueDuration polled at 9:33 AM returns a result of 0.6 hours. The value of 300 has been the same since 9:00 AM; 33 minutes converted to
hours is 0.6 hours.
Figure 177. Numeric Point configuration
Analytic charts and tables display the accumulated value duration times instead of the raw values from the data source history.
Figure 178. Chart showing the accumulated value
If the Value Duration Block needs to pass the results as a trend via the Out slot linked to a downstream block, change the Makes Trends property from its default, false, to true.