TS EN IEC 61124

TS EN IEC 61124 addresses reliability compliance testing under the assumption of a constant failure rate or constant failure intensity. It sets out how to structure test plans and their decision boundaries when the observed failure behaviour of a product or system is checked against a stated requirement. In practical terms, it belongs to the class of statistical acceptance methods used to judge whether field-like operating data are consistent with an expected reliability level.

How the main reliability measures are related

The standard is concerned with observed failure rate, failure intensity, mean time to failure (MTTF), and mean time between failures (MTBF). Its technical basis is the common reliability assumption that, over the accumulated test time, times to failure or operating times between failures are independent and identically exponentially distributed unless stated otherwise. That assumption leads to a constant hazard-type behaviour and supports plan-based pass/fail decisions rather than reliance on a single point estimate.

Test plan families covered by the document

• Truncated sequential probability ratio test (SPRT)
• Fixed time/failure terminated test (FTFT)
• Fixed calendar time terminated test without replacement
• Combined test

The standard also provides algorithms for designing these test plans with spreadsheet software and gives guidance on choosing among them. It does not cover general advice on planning, conducting, analysing, or reporting a test; those topics are directed to IEC 60300-3-5. Nor does it define test conditions, which are addressed in IEC 60605-2 and IEC 60300-3-5. In general engineering use, this kind of document helps translate a reliability requirement into a controlled statistical test procedure with predefined decision lines and stopping rules.