What is MTBF? What concepts are often mistakenly compared/drawn with it?
Mean Time Between Failures (MTBF) is the predicted elapsed time between inherent failures of a mechanical or electronic system, during normal system operation. MTBF can be calculated as the arithmetic mean (average) time between failures of a system.
This term is often confused with “DMTBF” and “LIFETIME”.
DMTBF represents Demonstrated Mean Time Between Failures. This is the way companies test MTBF in theory by speeding up product attrition rates to see where and when a product flaw will most likely appear. Because a regular MTBF test takes a long time and is very expensive, the industry often uses DMTBF to simulate user circumstances to get the test results sooner.
LIFETIME is the total amount of time that a product can be used under normal operation circumstances before it is no longer operational. The industry often takes the shortest life span component as the standard length of a complex product. In the case of power supply units, the capacitor is often taken as the benchmark when calculating the estimated total length of product life.
To sum up, MTBF≠DMTBF≠LIFE. These are three different concepts related to summarizing the total lifespan of a product and none of them can be precisely calculated to an accurate single number. Therefore, if you read some marketing information like “our product life span is long, with an MTBF of more than 10,000 hours,” then you need to realize that this is an estimated lifespan created with accelerated and controlled testing scenarios.