An instrumentation system that would comprise a remotely controllable and programmable low- voltage circuit breaker plus several electric- circuit-testing subsystems has been conceived, originally for use aboard a spacecraft during all phases of operation from pre-launch testing through launch, ascent, orbit, descent, and landing. The system could also be adapted to similar use aboard aircraft. In comparison with remotely controllable circuit breakers heretofore commercially available, this system would be smaller, less massive, and capable of performing more functions, as needed for aerospace applications.

The circuit breaker in this system could be set open or closed and could be monitored, all remotely. Trip current could be set at a specified value or could be made to follow a trip curve (a specified trip current as a function of time). In a typical application, there might be a requirement to set a lower trip current or lower trip-curve values to protect circuits during initial testing, and to set a default higher trip current during subsequent pre-launch and launch operations.

In the open state of the circuit breaker, one of the circuit-testing subsystems could obtain electrical-resistance readings on the load side as indications of whether faults are present, prior to switching the circuit breaker closed. Should a fault be detected, another circuit- testing subsystem could perform time-domain reflectometry, which would be helpful in locating the fault. On the power-line side, still another circuit-testing subsystem could take a voltage reading, as an indication of whether the proper voltage is present, prior to switching the circuit breaker closed.

The system would be contained in a housing, with input, output, and data/control connectors on the rear surface. All monitoring, control, and programming functions would ordinarily be performed from a remote console. On the front surface, there would be a push-button switch for optionally locally setting the circuit breaker in the open or closed state, plus a lamp that would provide a local visual indication of whether the circuit breaker was in the open (initially set), closed, or open (tripped) state.

The aforementioned monitoring, testing, state-setting, and trip-current-setting functions would be effected by circuitry on an integrated-circuit card inside the housing. Also on the card would be (1) input and output circuitry for remote monitoring and control and (2) a tag random-access memory as an electronic means of identifying the system by serial number, location, a reference designation, and operational characteristics.

This work was done by Terry Greenfield of ASRC Aerospace Corp. for Kennedy Space Center. For further information, contact the Kennedy Innovative Partnerships Program Office at (321) 861-7158. KSC-12742

NASA Tech Briefs Magazine

This article first appeared in the August, 2008 issue of NASA Tech Briefs Magazine.

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