The present invention relates generally to potential-continuity testers and more particularly to a relative potential-continuity tester for detecting faults in electrical systems.
In the past, various devices were developed for detecting continuity electrical systems by measuring or sensing the electrical conductance across the ends of the system's component conductors. These devices are generally classified as ohmmeters and one such device is shown in the U.S. Pat. No. 3,328,684 granted to S. Dorris. These devices were subject to a number of problems. First, in complex circuits, both ends of the conductor had to be traced out. Second, the conductor generally had to be disconnected from the remainder of the electrical system to prevent erroneous indications. Third, in large size electrical systems the device required long leads for connection to test conductors whose ends were far apart. And, fourth, poor accessibility to the conductors' ends often resulted in excessive fault detection time.
Various other devices were developed for detecting continuity by measuring or sensing electrical potential across the systems source and related conductors. These devices are generally classified as volt meters and such devices are shown in the U.S. Pat. No. 3,157,870 to J. S. Marino et al, the U.S. Pat. No. 3,311,907 to H. E. Teal, and U.S. Pat. No. 3,072,895 to B. A. Kaufman. These devices had the disadvantage of being incapable of indicating with one reading the difference between the next open or excessive resistance in a faulty circuit and a low source voltage in a good circuit. A second potential reading across the source itself was always necessary before the first reading could be meaningful. Further, while the first and second readings would indicate continuity in a first portion of the system from the source to a always necessary before the first reading could be meaningful. Further, while the first and second readings would indicate continuity in a first portion of the system from the source to a selected point, a third reading would be necessary to determine the continuity of the remainder of the circuit from the selected point back to the source.
A further device which was developed solely for determining voltage levels and thus indirectly continuity for electronic circuits is shown in the U.S. Pat. No. 3,525,939 granted to R. L. Cartmell. This device relates voltages at a selected point to a single, ground, potential and, while useful for detecting continuity in the ground-circuit portions of logic circuits, is subject to the same disadvantages enumerated for volt meter classification devices.
Neither the conductance sensing nor the potential sensing devices related the current flow and potential at the selected point to the electrical system's source to allow fault detection with a single reading.