Causal Reasoning and Rationalization in Electronics
This research attempts to formalize the type of causal arguments engineerings employ to understand circuit behavior. A causal argument consists of a sequence of changes to circuit quantities (called events), each of which is caused by precious events. The set of events that an individual event can directly cause is largely an artifact of the point of view taken to analyze the circuit. A particular causal argument does not rule out other possibly conflicting causal arguments for the same circuit. If the actual behavior of the circuit is know or determined by measurements, the correct argument can be identified. The selected argument is a rationalization for the observed behavior since it explains but does not guarantee the observed behavior. A causal analysis program QUAL has been implemented which determines the response of a circuit to changes in input signals. It operates with a simple four valued arithmetic of unknown, unchanging, increasing and decreasing. This program is used to illustrate the applicability of causal reasoning to circuit recognition, algebraic analysis, troubleshooting and design.