Fault occurrence displaying system, for use with machinery, which automatically signals and initially displays only a first-occurring of perhaps several machine faults which occasion machine shut-down. The system includes means for automatically signaling and displaying both system failure and proper system functioning as well as means automatically operative to hold a fault signal on until manually turned off and means to hold successive fault signals inoperative until the first-occurring fault...

An electrochemical sensor system includes an electrode assembly that produces a DC signal as a function of a parameter of interest sensed by the electrode system. An AC signal is applied via an electrode to the conductor fluid in which the electrode system is disposed and an AC signal detector is connected to the DC circuitry. A threshold circuit responsive to the output of the AC signal detector indicates fault in the electrochemical sensor system whenever the AC signal detector has an output o...

An alarm or fault detection system for in service electronic equipment which is not electrically connected to the equipment. A chemical tracer element which is responsive to the application of a certain force, physical stress, electrical stress, or heat, for example, is embedded in the equipment or portion thereof that is to be monitored. When the equipment's functional tolerance limit of the certain force is reached, the tracer element is released in a gaseous form. Presence of the tracer eleme...

A relay for protecting three-phase, wye-connected circuits by monitoring neutral voltage. To prevent relay operation during normal unbalanced conditions, the current input to each phase is monitored, and relay operation enabled only when three currents are present.

A ground fault protector for use with an A. C. electrical power distribution system and particularly suited for operation at current levels in the range of 150 to 1,200 amperes. A ground fault protector for sensing fault current in the ground strap and tripping the circuit breaker switch to open the power lines. A magnetically operated reed switch mounted at the ground strap and a solid state circuit actuated by reed switch closure to energize the breaker trip coil, with current sensitivity prov...

A time division multiplex fault detector employs certain time slots in each multiple's frame to test the highways and gates as well as to set storage elements which control the systems and other circuits.

A television equipment consisting of a number of sub units includes fault indicating and locating apparatus. The fault indicating and locating apparatus comprises a display device having raster scanning in synchronism with the television equipment scanning raster and predetermined signals are applied to different equipment sub-units for different fractions of the television raster line, and field, periods. Signals that have been passed through different combinations of sub-units are applied to s...

A fault in an insulated electrical cable of known propagation velocity is located by applying to the cable a voltage at about rated cable voltage to ionize material in the region of the fault and concurrently applying a high powered D.C. pulse having an abrupt onset to the cable at about a peak of the alternating voltage to produce reflections from the mismatch at the location of the ionized material. The time interval between application of the D.C. pulse and the return of the reflection is the...

A differential transformer for sensing the fault current in a ground fault interrupter includes a magnet toroid with the power leads extending through it in a co-axial arrangement to provide single turn primary conductors. Stray current resulting from uneven placement of the power conductors within the toroid is thereby avoided; the relation of each of the coaxial conductors to the toroid is the same. Single turn coaxial conductors are highly advantageous in providing a miniaturized differential...

A ground fault detector providing protection from leakage current to ground by sensing unbalance in supply and neutral conductor currents to actuate a circuit breaker. A solid state circuit including amplifier and detector and having the unbalance signal of a current transformer as an input for energizing a trip coil of the breaker when the unbalance current exceeds a predetermined level. Improved circuitry providing temperature compensation, insensitivity to turn on and other transients and noi...