At the design level, create a checklist attribute named “DetectionMapAttr=XXXXX” (where XXXXX is replaced with the name of the attribute containing the test categories,in this case “BIT”).
Add an entry for each category that you wish to map (in this case IBIT and PBIT), as well as an optional entry called “DefaultMapping” to be used for tests whose categories are not included in the list. Assign the desired detection ratings as values.
The excerpt below shows how detection ratings appear when calculated using the attribute method. Use independent-mode diagnostics when you wish to base detection ratings on all tests that could possibly detect each failure. The detection rating will be based on the test whose category attribute has the highest assigned value. If, on the other hand, you wish for the rating to be based on the tests in an ordered sequence that detect each given failure, use standard diagnostics.
In the example above, for tests that were both PBIT and IBIT, the value 7 was assigned (the greater of the values for PBIT and IBIT). The failure that is only detectable using SBIT, however, was assigned the default mapping value of 2 (since there is no entry for SBIT in the mapping table). Finally, notice that non-detected failures are automatically assigned a detection rating of 10.
The severity, occurrence and detection factors that are used to calculate the Risk Priority Number (RPN) are calculated separately from the individual severity, occurrence and detection ratings that appear in their own columns.
This means that—if you wish—you can include the RPN column without having to also include the columns for the three ratings.
In this example, the existence of the attribute “DetectionMapAttr=BIT” caused the RPN calculation to utilize attribute-based mapping—even though neither the BIT categories nor the detection ratings appear anywhere in the FMECA.
As with the severity and occurrence ratings, you can override the calculated detection rating by creating a DetectionRating checklist Attribute and then assigning values for each failure in the FMECA.
