Knowledge Base
1.- New .mtbf files extension, replacing the .bqr extension! From now, all the files created by the CARE-Manager module will have a .mtbf extension. Previous projects, with the .bqr extension, are still usable. To use those files, outside of the user interface a user may double click on them, or within the software a user can select an "Open" menu, and then select the option of "*.mtbf ;*.bqr". After that action, all previous projects will be visible. Then simply select the desirable file and press on "Open" button. 2.- Creating csv files from Zuken Redac data base In order to create a csv file from Zuken Redac EDA program please follow the instructions:
1. Use new ZR-Product, System-Design
2. Create report Component Browse -> CSV format.
3. Import this file to CARE.
If your CSV file includes the following columns titles in the second line, they will be imported to CARE:
reference -> Reference Designator (RefDes)
partname -> Part Number
Value -> Catalog Number
thm_power_diss -> Power Mean
shortPrt -> Description (1)
thm_power_max -> Description [Pm= ] (2)
Tolerance -> Description (3). 3.- NT Administrator/user privilege If CARE is installed under Administrator privilege the program works.
If CARE is installed under a user privilege the program doesn't works.
In this case you must give the user the same privilege for the "CARE Suite" as for the Administrator. 4.- Defining Template to create new project file The "Customer Template Generator" allows a user to select all the global and environmental settings for all of his projects only once, and then using it throughout all of his projects. [ More]5.- Adding a new component from CARE - Manager (MTBF) to FMECA tree throw CDB, after file creation. After creating an MTBF design inside of CARE-Manager, a FMECA tree is built throw CDB. but what if a new component was added to the MTBF tree? How should this change be reflected in FMECA? [ More]
Forum
MTBF is defined as Mean Time Between Failures and MTTF - Mean time to failure. Both are measures of reliability that are defined statistically as the number of hours a component, assembly or system will operate before it fails. The MTBF data for a product can be derived from laboratory testing, or prediction models such as MIL-HDBK-217 (the Military Handbook for Reliability Prediction of Electronic Equipment, published by the U.S. Department of Defense), Bellcore and others. F.R = 1/ MTBF. The failure rate is generally used as an indicator of reliability. The failure rate is the proportion of failures that occur within a specific time. The failure rate also changes over time.
*Note: This formula is correct only when the distribution is exponential.
A more manageable values which is done by scaling the failure rate so that f(t) is the failure (%) per 1 x 109 is done by scaling the failure rate so that f(t) is the failure (%) per 1 x 109.
This is known as a FIT: 1 Failure / 1 x 109 I am looking for an equation to establish a confidence level of MTBF in a test environment For the exponential distribution, two situations must to be considered for estimating confidence intervals:
· The test in run until a pre assigned number of failures ( r* ) occurs
· The test is stopped after a pre assigned number of test hours ( t* ) is accumulated
The formula for the confidence intervals is based in the chi – square distribution.
The equations for confidence limits (Exponential distribution) are showing above.[ More]Is there any way to calculate the number of expected failures in one year based on the MTBF The failure rate is defined as the number of failures experienced or expected for a device divided by the total equipment operating time. For constant failure rate items, i.e. exponentially distributed failures, the failure rate is the numerical inverse of the mean time between failures (MTBF).[ More]Where can I find standard MTBF values for equipment and systems when the supplier of the equipment has none? If you want to perform reliability prediction you must know data about the components, the electronic data sheet is one of the best source to know the different parameter to calculate the MTBF values. For example, if you want to calculate the MTBF of IC, MIL-HDBK-217 approach, you need to know parameters like: Package, pin number, power max dissipated, thermal resistance, etc. [ More]If I have MTBF result in one of the prediction methods, what are the factors to translate the result into a different prediction method? There are no such factors! If some product’s MTBF was calculated in some prediction method, for example Bellcore, there is no factor that can multiply this number to transform it into a result in Mil-HDBK-S217 prediction method. We have an MTBF result at some specific temperature. But some more MTBF results in different temperatures are required. Is there any way to find such an MTBF, or should we start from the beginning?: In the case of environment transactions, there are factors that can be used if some result should be revised in a different temperature or environment as well. What is the best prediction method to perform an MTBF calculation with? There is no such a method. The selection of the most suitable prediction method should be done based on the customer’s field of business. The relevant factors that should be taken under consideration are the type of the product, such as electronic equipment or mechanical assembly, the possible spheres of use for the product, such as laboratory equipment or perhaps a fired missile, and the specific requirements of the customer.
| Reliability Block Diagram - RBD |
The system has redundant blocks. Is a reliability calculation a sum of the Failure Rates of all blocks? No. In a case of complex systems, including redundant blocks, a MTBCF (Mean Time Between Critical failures) calculation should be performed. Such a calculation takes under account only critical blocks, which failures will cause a system’s malfunction. Some blocks’ failures won’t cause a system’s malfunction, and thus should not be taken under consideration during the reliability calculation of such a system. The MTBCF result reflects more accurately the actual reliability of a complex system. Nevertheless, a MTBF calculation should be done as well, in order to receive individual Failure Rates of each component.
I would like you help me to draw or graphic about MTBF. MTTR (Mean time to repair) is include on MTBF? First, The MTBF parameter is defined as the total functioning life of a population of an item during a specific measurement interval, divided by the total number of failures within the population during that interval. [ More]How to predict MTTF of CPU and other cards using the MIL-HDBK-217F? MTTF is a measure of reliability for non-repairable systems. However, MTBF is commonly used for both non-repairable and repairable items.
The first and the logical way is request the MTBF of this CPU from the manufacturer. [ More].How to calculate the MTBF & MTTR values. First, to calculate MTBF by MTBF Software, there are several ways.
The part stress analysis method is used in the design phase when individual part information and design stress data are known. The method require the use of defined models that include electrical and mechanical stress factors, environmental factors, duty cycle, etc.[ More]What is the difference between MTBCF and MTTCF? The MTTCF (Mean Time To Critical Failures) analysis should be made when there is no cyclicality of the failures, while the MTBCF (Meant Time Between Critical Failures) analysis should be made when such cyclicality exists. The Failure Rates of the regular MTBF calculation and the Failure Rate of the FMECA calculation were not the same! Probably no mistake was made. There is no necessity for the both results to be the same. Mostly, the MTBF calculation is made upon hardware tree of the system (based on the Bill Of Materials), while FMECA performs analyze for a logical tree. While in the MTBF calculation every Failure Rate of each component is simply summed up to the general system’s failure rate, in the FMECA each component/function may affect on several other items. Along with a fact that probabilities of all events are taken under consideration in the FMECA analysis, there is nothing unusual in the different results that might be received in both cases.
What is the benefit of Testability Analysis? The Testability Analysis allows mapping the percentage of the faults detection and isolations by the automatic tests available in the system (Built In Tests). Such an analysis should be performed after the FMECA analysis was made, and thus all the failures of the system are known. The Testability Analysis displays the percentage of the detected and the undetected faults; displays the isolation level of a system, i.e. if a failure happened, and we know it happened, how accurately we can point to a failed block. This analysis shows the percentage of the False alarm and the BIT fails percentage as well.
| Mean Time to Repair - MTTR |
I have MTTR values of a system elements. How do I can calculate MTTR for the whole system The MTTR is defined as the mean time required to complete a maintenance action, i.e., total maintenance downtime divided by total maintenance actions for a given period of time, given as [ More].
|
