Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – For fault location
Reexamination Certificate
1998-02-12
2001-05-01
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
For fault location
C324S529000, C324S537000
Reexamination Certificate
active
06225810
ABSTRACT:
INTRODUCTION
The present invention is an improvement over U.S. Pat. No. 5,378,992 issued Jan. 3, 1995, assigned to The Boeing Company, titled “Shield Integrity Monitor”. The '992 patent describes a method and apparatus for non-invasively measuring the resistance of electrical cable shielding which connects to a common ground, e.g., aircraft structure. The electrical cable and the aircraft structure to which it attaches from a continuous loop through which current can flow. A known low-level AC electrical voltage is induced around this loop via a clamp-on toroidal electrical coupler, and the resulting loop current is measured by another clamp-on toroidal coupler. The complex ratio of the current induced in the loop to the loop voltage gives the loop impedance, the real, resistive, part of which is an indication of the integrity of the electrical shielding and it's bonding to aircraft structure. In addition, a joint measurement mode is provided in which a pair of probes make electrical contact onto two parts of the loop being tested. The ratio of the measured voltage difference across these probes to the current induced in the loop provides the resistance between the two probes. These probes are used to identify where in the loop the problem lies.
Problem Solved by This Invention
The present invention is an improvement over U.S. Pat. No. 5,378,992 and removes the need for calibration of the instrument, and simplifies the computations needed to generate a measurement. The hereinafter described system allows for easier use by the mechanic in the shop or in the field.
BACKGROUND INFORMATION
A previous non-invasive shield continuity tester shown in U.S. Pat. No. 5,378,992 utilized laboratory test equipment in a prototype embodiment, e.g., a network analyzer and a P.C. Such equipment can also be utilized to determine the existence of corrosion. This embodiment was cumbersome in that it required three operators viz. one at the system with a headset, one at the aircraft with a headset, and one hooking and unhooking the system to the aircraft. Consequently, a development program commenced to overcome these deficiencies and develop further features which would permit a single operator to test an entire aircraft cable system in the field.
BRIEF SUMMARY OF THE INVENTION
A loop resistance tester (LRT) for shield integrity testing. The tester utilizes a drive current probe having two windings, the extra winding placed on the drive current probe being utilized to measure the voltage actually forced on the shield of the shielded wiring.
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Deventer Bruce Van
Eaton Mervin E.
Godo Erik L.
Gonder John F.
Gardner Conrad O.
Kerveros James
Metjahic Safet
The Boeing Company
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