Latency Page (SAE Events Only)

Windchill Risk and Reliability Desktop Help > Windchill FTA > Fault Tree Object Properties > Gate or Event Properties > Latency Page (SAE Events Only)

The Latency page is shown in the Properties window only for events in SAE trees. For these properties to be available, Failure rate/MTBF must be selected as the model on the event’s Calculation Data page. Additionally, the event cannot be linked to a Markov diagram. The following table describes these properties, which are used to indicate if latent failures can occur and whether a monitor is used to detect them.

Property	Description
Latent Failures	Indicates whether this event is subject to latent failures, which are failures that are not detected or annunciated when they occur. When this checkbox is cleared (default), this event is not subject to latent failures, which means no other properties on this page are available. When this checkbox is selected, this item is subject to latent failures, which means that other properties become available so that you can supply information about how to check for and detect them.
Check Interval	The amount of time in hours between inspecting for latent failures. The default is 0.
Failure Detection Percent	The percentage of time that the latent failure is detected. You enter a value from 0 to 100. For example, if the latent failure is detected 90 percent of the time, you would enter 90. The default is 0.
Detection Method	Indicates how the latent failure is detected prior to the check interval. The choices are: • Self Checking. When selected (default), latent failures are detected through self tests. • Monitored. When selected, latent failures are detected through dedicated hardware circuitry, software code, or various test methods. You then supply information about this detection method, which is referred to as a monitor, in the additional properties that become available. • Unmonitored. When selected, a value of 0 is used for Failure Detection Percent.
Monitor The properties under this heading are available only when Monitored is selected for Detection Method.
Turn off monitor	Indicates whether to use monitor properties in calculations. When this checkbox is cleared (default), monitor properties are used. The properties available depend on the selections you make. For example, if you select a common monitor, other monitor properties are unavailable. When this checkbox is selected, monitor properties are not used, and other monitor properties are unavailable.
Common Monitor	Provides for selecting a common monitor from all those inserted in FTA Common Monitors Library files. Common monitors are listed in alphabetical order. If multiple common monitors are assigned the same name, only one is listed. The parameters used are from the first one found based on the library search order. If you select the blank choice to remove the common monitor selection, the property values for the last common monitor are kept. For more information, see FTA Common Monitors Library Files.
Monitor Failure Rate	The failure rate of the monitor. In the System file properties, General > Failure Rate Multiplier specifies the units. For more information, see General System File Properties.
Scrub Time	The amount of time in hours between verifying that the monitor is operating properly. The default is 0.
Scrub Verification Percent	The percentage of time that scrub verification detects and corrects monitor failures. You enter a value from 0 to 100. For example if scrub verification detects and corrects 90 percent of the monitor failures, you would enter 90. The default is 0.
Monitor Check Interval	The amount of time in hours between inspecting the monitor for latent failures. The default is 0.
	When clicked, you can save the monitor properties specified for the event to a new common monitor in the first FTA Common Monitors Library file to which you have write permission.