====== Equipment Failure Detector ======

{{:en:mervis-ide:35-help:failuredetector.png}}

===== Function Block Name =====

Lib.Mervis.v1_1.FailureDetector

===== Description =====

Core block used to evaluate equipment operation and detect failures.

===== Required Project References =====

  * Lib.Mervis

===== Block Usage Restrictions =====

None - current standard block.

===== Usage in ST =====

<code>
program test
    var
        failuredetector: lib.mervis.v1_1.FailureDetector;
    end_var

    failuredetector();
end_program
</code>

===== Input and Output Description =====

|Inputs      |Name    |Data type|Retain|Must be connected|Description|
|Demand      |bool    |No       |Yes   |Operating demand |           |
|Feedback    |bool    |No       |Yes   |Running feedback |           |
|Failure     |bool    |No       |Yes   |Failure signal input|      |
|Delay       |time    |No       |No    |Waiting interval for active running feedback| |
|CountLimit  |uint    |No       |No    |Number of consecutive failures required to trigger a persistent alarm| |
|Timeout     |time    |No       |No    |Delay before restarting|           |


|Outputs       |Name                         |Data type    |Description|
|FailureOutput |[[AlarmTrigger.htm|AlarmTrigger]]|Alarm output|           |

===== Detailed Function Description =====

The block evaluates equipment operation and generates a trigger condition for alarm generation. When the //Demand// command is active, the //Feedback// signal is monitored. If it does not become active within the time specified by the //Delay// input, an alarm is generated.

An alarm is also generated when the //Failure// input is activated. If the number of consecutive failures (separated by activation and deactivation of the command) is less than //CountLimit//, an alarm with automatic reset is generated. Otherwise, manual intervention is required to reset the alarm.

The alarm remains active for the period specified by the //Timeout// parameter. If startup is successful, the failure counter is reset.

The block generates alarms with the following priorities:

  * //32// - alarm requiring external intervention
  * //33// - alarm with automatic reset