Categories
Statistics
Flag Counter
Since 08.08.2014
Counts only, if "DNT = disabled".

Your IP is 44.213.60.33
ec2-44-213-60-33.compute-1.a
Info
Valid HTML 4.01 Transitional Creative Commons Lizenzvertrag
rss
เราจะทำแบบวิศวกรผู้ยิ่งใหญ่
We love the King
23. July 2024
Your valuable opinion :
3 stars

Avg. 3.00 from 8 votes.



MTBF-1.php    5152 Bytes    23-04-2024 11:07:11


Mean Time To Failure • Reliability Considerations


How to calculate the Reliability of your circuit




MTBF




FITS • λ




FIT means Failure In Time. It indicates, how many units fail within a certain timespan e.g. 10^9 hours.

1 FIT = 1 Failure in 109 hours

As the timespan may vary, it is recommended to indicated it. (109 hours is widely used)
Measuring the number of failures over time provides a failure rate : λ.




MTBF • MTTF




The Mean Time Between Failure (MTBF), or for components, the Mean Time To Failure (MTTF) is the distribution for a population of parts. MTTF is the reciprocal of the failure rate.

MTBF = 1 / λ




1) Collect Data




In a first step, you must collect all FIT's from every component in your circuit. This data mayst be delivered by the manufacturer, obtained by simulation or by own measurement.

It is good practice to do this with the spread-sheet of your choice. By that, you can calculate the sum of all FITs times their occurence.



And yes : Manufacturers don't like to publish their FITs. So there is some guess-work involved.




2) Probability for Failure




With the above, we can now calculate the Probability for Failure = F(t) and the Probability for Survivor = R(t).

R(t) = exp(-λ * t)

In our example this becomes :

R(5 years) = exp(-3328.3 * 109(per hour) * 5 (years) * 365 (days/year) * 24 (hours/day)

= 0.8643 or 86.43 %.

And F(t) = 1 - R(t) becomes : F(5 years) = 0.1357 or 13.57 %




3) MTTF : Mean Time to Failure




MTTF = 1 / λ

In our example this becomes :

MTTF = 1 * 109 / 3328.3 = 300453.7 hours or 34.4 years.




✈ Share your thoughts



The webmaster does not read these comments regularely. Urgent questions should be send via email. Ads or links to completely uncorrelated things will be removed.


Your Browser says that you allow tracking. Mayst we suggest that you check that DNT thing ?

 
t1 = 6585 d

t2 = 150 ms

★ ★ ★  Copyright © 2006 - 2024 by changpuak.ch  ★ ★ ★

Impressum