>>I seem to recall that the military wants to see ambient scans with at
>>least 6dB under any limit. Kind of a inside out measurement
>>uncertainty?.
>Yes, it's a sort of insurance against a 6 dB favourable error. But the
>point is that it's FAR easier to cope with in practice, and it may well
>give a more dependable assurance of compliance than a complex
>uncertainty assessment.
Well you can call this a 6dB trick but in fact is the implementation
into the daily use of MU. Just that it has been calculated by
someone else, and assumed to be true for every test set up.
MU is not difficult, the calculations do not involve more then:
1. characterization of the fault contributor, result into division factor
2. square the obtained value
3. do this for all contributions
4. add up all factors
5. take the root and multiply by 2 = total expanded uncertainty
That’s all there is. The tricky part is the characterization in type of
error.
Google for probability distribution and type A or type B uncertainty if you
want to learn.
Gert Gremmen
ce-testm qualified testing
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