1. Field of the Invention
The present invention relates to a system for testing the integrity of electric wiring.
2. Discussion of Prior Art
The wiring within electronic systems may bum through or break, becoming an `open circuit`, or may bum through electrical insulating material to come in contact with other conducting electrical elements causing a short circuit.
Many times it is impossible to detect open or short circuits by monitoring a signal of the wiring. This occurs in systems where a `0` voltage level is a valid signal, but also occurs during an open circuit. Similarly, a short circuit may exhibit a voltage which is also a valid signal value.
A wire may be tested for continuity by connecting one end to a current or voltage source, connecting the other end to a known load or measurement device, and observing the value of current that flows or the voltage that appears at the load. Such tests may be done periodically or when an open circuit is suspected. These tests may be done manually, or by dedicated automatic circuitry. They may be performed in sections to isolate faulty segments. The key drawback of such tests is that they require interrupting the normal signal path, so that for the duration of the test, the desired signal is not transmitted.
A similar method may be employed to test for short circuits, by driving a wire with a known signal. A short circuit may be deduced by the presence of a response signal on a wire which is not being driven. A short circuit may also be indirectly deduced from an incorrect response signal of the driven wire. Again, the difficulty is the disturbance of the signal path for the duration of the tests.
Determining open and short circuits through manual means becomes very difficult or impossible in remote or hazardous environments such as on satellites, aircraft guidance systems, in nuclear reactor cores, deep within drilling wells, in constricted or hidden enclosures. Automation of the above described tests requires the addition of circuitry with attendant increase in failure rate, cost, power dissipation, and size.
Also, without testing, the system may be operated with defective wiring, leading to false conclusions and undetected hazards.
Some wiring in an electronic system is more sensitive than others. A short or open circuit of wiring used in sensing the operation of a large current consuming device, such as a motor, causes a controller to receive incorrect information about the status of the system. This causes the controller to overlook an overload situation causing damage to system components. This may occur even if protected by circuit breakers if they do not cut the power quickly enough, or if the faulty wiring is associated with operation of the circuit breaker.
Currently there is a need for wire test system which automatically determines the integrity of electrical wiring.