TransitionSwitch (BTransitionSwitchBlock)
Test In value (both value and status) equals the Target In value and whether the Test In value has changed value or status from its prior value. This block supports both value and trend requests.
This block is similar to the Cov Switch Block with the added criterion that the value of Test In equals the value of Target In. The Cov Switch Block detects any change in value (both value and status), whereas, you may configure this block to only detect a change in value
from false to true.
For value requests, the block requests a trend from Test In using the Value Search Limit property as the time range prior to the current station time, and then compares the last record from the trend to Test In value. If the value of Test In equals the value of Target In and the value of Target In changed from the prior value, the block outputs the True In value, otherwise it outputs the False In value. If the True In slot is not linked, the block outputs the default numeric value of true, one (1). If the False In slot is not linked, the block outputs the default numeric value of false, zero (0).
Figure 209. Transition Switch 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 either the True In or False In value based on evaluating the Boolean condition.
|
| Test In | value slot | Links from the output of other logic blocks or data sources to supply one or more input values to be tested for validity in the logic block. |
| Target in | value slot | Links from the output of other logic blocks or data sources to supply one or more input values to be tested for validity in the logic block. |
| True In | optional value slot (defaults to True if not linked) | Links from the output of other logic blocks or data sources to supply one or more valid values to the logic block. |
| False In | optional value slot (defaults to False if not linked) | Links from the output of other logic blocks or data sources to supply one or more invalid values to a logic block. |
| Value Search Limit | hours minutes seconds (defaults to 1 hour) | Defines how far back in time to request a trend from the Test In (input) for value requests. The system compares the last record of this trend to the result of a value request on the Test In to determine if there was a change of value or status.
|
Example
Consider a Boolean point with either a COV or interval history for enabling a system, which is tagged with hs:enableCmd and a:a marker tags. An algorithm with a Transition Switch Block can determine when the system enable command changes state from false to true.
Figure 210. Transition Switch algorithm
A numeric point with an Analytic Proxy Ext is configured with Data = alg:TransitionSwitch, Time Range = yesterday, Rollup = Sum and Interval = Fifteen Minutes. The algorithm result is the sum of the true (1) and false (0) values during the time range, which indicates how many times
the system enable command changed state from false to true.
Figure 211. Configuration
