JPH05289903

PURPOSE:To obtain effective diasgnostic results even when information relating to a fault is not sufficiently enough at the time of using a fault diagnostic method (FTA) by using a tree expressing fault causal relation having the probability of fault causes on its nodes. CONSTITUTION:A numeric value 15D expressing probability indicates the statistically calculated easiness of generation of a phenomenon due to faults generated in the past. For instance, when a phenomenon 159 of [no cooling (no running)] occurs, the probability of generation of a phenomenon 15A of [immediately after installation] is 30%, the probability of the generation of a phenomenon 15B of [on the way of running] is 50% and the probability of a phenomenon 15C of [frequently] is 20%. When the probability concept is adopted to the FTA, a diagnosing operator can execute rational estimation tentatively doubting that a phenomenon having high probability may be the cause of the fault, so that rapid decision and processing can be attained.