Fault diagnosis of nonlinear analog circuits. Volume 4: An isolation algorithm for the analog fault dictionary

A new approach for fault location in an analog fault dictionary has been adopted on the basis of quantizing circuit responses. The possibility of quantization is offered by faults having nearly the same effect on some test measurements. This produces multivalued logic responses which can be manipulated logically to obtain decision rules for fault location. A logical isolation algorithm has been introduced to form a dictionary for hard fault diagnosis using d.c. voltage measurements. The dictionary consists of tables containing voltage ranges of quantized response and numerical codes identifying different faults inthe dictionary. The test measurements chosen by the algorithm are free from redundancy and provide the maximum fault isolation capability of all initially chosen measurements. The algorithm can be easily implemented with some extra software added to the circuit simulator used in fault simulation. Hardware implementation of a logical isolation ATE is simple and efficient compared to a least squares based dictionary. The algorithm has been extended to handle multiple test input conditions.