This paper proposes a novel method to estimate
the influence of hard-fault in linear-analogue circuit system
based on the measurement of voltage phasor with assistant
branch introduced. Furthermore, a new fault diagnosis strategy
based on the voltage phasor modeling is established, and the
tolerance influence on the corresponding voltage measurement
is also discussed. The actual analogue circuit test shows us
that the proposed method is effective and reliable to locate the
accurate fault signature in voltage measurement for the fault
diagnosis. As a matter of fact, it includes both the amplitude and
phase information in a complex value form when the linear-analogue
circuit is under the AC test. Besides, it can be also
applied to ambiguous groups and the sensitive test-frequencies
determination in the process of fault diagnosis,while the effectiveness
of multifrequencies test has also been testified through
test-frequencies sweeping investigation and the maximum error
evaluation of fault component value in the second circuit example
