Change of the reliability of electrical measuring instruments during their long operation

Conclusions

• 1. The failure rate of measuring instruments is not constant in time. During 5–10 years its values for the investigated instruments changed by a factor of 10–15 (see Fig. 2).

• 2. For characterization of the reliability of measuring instruments during the time of their operation (comprising, as practice shows, 4–5 interrepair periods) the technical documents must indicate not only the values ofw ₀ during the first year of life of the instrument but also the values of v during subsequent years.

• 3. The failure rate for various types of measuring instruments can both increase and decrease. The changes are so great that a determination of the failure rate by factory tests, even if these tests are conducted for an entire calendar year, does not reveal the values or even the trend ot its change which will be observed during real subsequent operation of the instrument.

• 4. For characterizing the behavior of instruments during their entire operating period it is necessary to determine and standardize the values ofw ₀ and v, which should be obtained from the data of annual checks conducted by institutions of the State Committee for Standards.