A technique for analog fault diagnosis using element modulation

The authors describe a novel branch fault-diagnosis technique which requires a single excitation source at one test frequency for solving branch-diagnosis equations. Linearly independent branch-diagnosis equations are constructed by modulating selected network elements. A network element whose value can be varied in a controlled fashion is defined as a modulated element. It is assumed for simplicity that all modulated devices in the network under test have two states (a state is a predefined element value). A subset of the network elements is modulated. Necessary and sufficient conditions for the diagnosis of at least q+1 branch elements at faulty circuit nodes have been derived for a general network where q network elements are modulated. An approximate upper bound on this system of equations is also derived. As an example, the proposed technique is applied to a resistive circuit