DC

diagnostic coverage

Fractional decrease in the probability of dangerous hardware failures resulting from the operation of the automatic diagnostic tests

(definition IEC 61508)

The fraction of the possible dangerous failures λ_D is divided into failures which are detected by diagnostics and failures which remain undetected.

λ_D=λ_DD+λ_DU

The diagnostic coverage (DC) defines the fraction of the dangerous failures which are detected.

λ_DD=λ_D • DC

λ_DU=λ_D • (1-DC)

The definition may also be represented in terms of the following equation, where DC is the diagnostic coverage, λ_DD is the probability of detected dangerous failures and λ_D total is the probability of total dangerous failures: