Abstract: Each of the either normally closed or normally open switches, in an n out of m voted power interface circuit having parallel connected groups of serially connected switches, is shunted by a high impedance resistor to form a leakage path through each group of switches. A detector associated with each group of switches, and responsive to the change of impedance produced by actuation of a resistor shunted switch in the group, generates an output signal, preferably a one bit digital signal, indicative of the state of the switches in the group in response to a sequence of test signals which selectively actuate fewer switches than are required to actuate the load controlled by the power interface. Compensation for large variations in supply voltage is provided by incorporating each group of switches into a resistance measuring bridge circuit in which the digital output signal is generated by a comparator connected across the bridge. Preferably, the bridge circuits share common reference voltage generating legs.

Abstract: A power interface circuit for normally deenergized loads includes the capability to test the operation and connections thereof without any possibility of accidental activation of the load. Three input signals may be received by the power interface circuit which supplies power to a load if two out of three of the input signals indicates activation of the load. A normally closed switch which ordinarily provides power directly to the voter is opened during testing so that the voter is supplied with a reduced power that is insufficient to activate the load. The normally closed switch is closed if any of the input signals indicate activation of the load. Current sensors are included in the power interface circuit to detect all possible logic combinations for activating the load and to detect the operation of the normally closed switch.

Abstract: An arrangement for detecting faults in automatic test systems of the type wherein test points in a unit under test are connected to test instruments by the programmed closure of electromechanical relay contacts. Respective contacts of the relays are connected to each other and, during periods intermediate of the closure of the relays, a detector circuit is coupled to the interconnected relay contacts. The detector circuit compares a voltage or resistance present on the interconnected relay contacts to a threshold. In one embodiment, if a difference between a signal on the interconnected relay contacts and the threshold persists for a predetermined period, an interrupt signal is generated which prevents further closures of the relays. In this manner, catastrophic failures of the unit under test and the test instruments are prevented.

Abstract: An electric field detector which comprises means for generating a linearly polarized light, a polarizing element including a ) Pockels cell made from a Z-cutting quartz which transmits the polarized light toward a Z-direction and changes the phase difference of two light components of a crystal in response to the magnitude of the electric field strength. The electric field detector of the invention can be widely used in measuring conditions of an electrical machine.

Abstract: The invention relates to a testing and evaluating circuit for a proximity itch suitable for testing and provided as an element of a machine control means; associated with the proximity switch is a control circuit, by which the proximity switch is alternately switchable between its two operating conditions to generate a timed output signal with a given frequency, an evaluating circuit being provided, by which a clear signal indicating fault-free operation is producable for the duration of a timed output signal from the proximity switch and by which a blocking signal for the machine control means, indicating a fault, is producable in the absence of changes in the potential of the output signal from the proximity switch. The evaluating circuit preferably comprises a relay circuit, to which the output signal from the proximity switch or a signal derived from this is fed via a transformer.

Abstract: In the testing of dry circuit contacts, a constant current source is applied to the contacts. The open circuit voltage of the source is set to a predetermined maximum value and then the short circuit current at the contacts measured. If the current value is below a predetermined maximum value, the voltage of the source is increased to bring the short-circuit current to the predetermined value. The voltage drop across the contacts is then measured and the contact resistance calculated. This arrangement makes adjustments to take into account variations in the test circuit, such as different lead lengths and other variables, without subjecting the contacts at any time to an open circuit voltage or short circuit current above maximum values.

Abstract: In a method of and apparatus for synthetic testing of a multi-break circuit breaker having a metallic tank and a series connection of interrupter units, and a non-grounded and a grounded lead conductors connected to the first and the second ends of the series connection, a short-circuit current is made to flow through the series connection, the circuit breaker is then operated, and upon completion of the interruption of the current, a first transient recovery voltage is supplied to the non-grounded lead conductor and is applied, in effect, across a first one of the interrupter units at the second end or across a train of interrupter units including said first one of the interrupter unit, and, simultaneously, a second transient recovery voltage is supplied to the tank, the first and the second transient recovery voltages having the same polarity and the second transient recovery voltage having substantially the same magnitude as the whole transient recovery voltage to be applied across all the interrupter unit

Abstract: A trip system comprises groups of three switches, each group being responsive to a single trip initiating event and each switch switching a different phase of a three phase power supply. Three trip actuators are each connected between different pairs of switches. Malfunction of a single switch in any group will not cause a trip to occur while concurrent operation of two or more switches in any group will cause a trip.

Abstract: A means for physically opening and closing electrical contacts to check their integrity for safety systems is provided. Contact means are cycled by the movement of two relatively moveable parts and the actual physical operation of the contacts is checked. The system is latched in its operable position by reversing the energization of an electromagnet which was used to unlatch or start the checking sequence.

Abstract: A test circuit for testing the circuit making or circuit breaking capability of a high voltage apparatus includes a high current source in a high current circuit and a high voltage source in a high voltage circuit. The apparatus to be tested is disposed in the high voltage circuit, and a switch with an explosive actuator is provided in the high current circuit to connect the apparatus thereto during testing. The explosive actuator is connected with a voltage source in the high voltage circuit for ignition thereof by the preignition of the tested apparatus.

Abstract: A method and apparatus for testing print elements of a printer, such as a belt printer, in which the print element operating circuits are energized at an energy level insufficient to cause printing but sufficient to generate feedback signals for checking operativeness by a microprocessor.

Abstract: An arrangement for testing relay contacts of a signal distributor is disclosed. The output relay contacts are coupled via isolation diodes to a common circuit node and the input relay contacts are coupled to a second node. A potential is applied to the first node through the diodes and contacts to a single scan point and selective operation of each distributor relay can be verified at the scan point. By reversing the nodes, the integrity of the diodes can be checked. Make, break, and transfer contacts are tested.

Abstract: Apparatus for detecting the presence of contamination films and foreign material on the conducting fingers of a circuit board. The apparatus includes a guide block assembly (11) designed to receive and momentarily hold a circuit board (100) and a spring biased hold down bar (25) for securely holding the circuit board in the guide block assembly. The apparatus further includes apparatus (23, 31) for use in positioning a plurality of probe assemblies (33) to simultaneously engage a pair of electrodes (330) with each one of the circuit board conducting fingers (101). A controller (43) enables switch apparatus (42) to selectively connect each pair of electrodes with electrical resistance measuring apparatus (50) to measure the resistance of any contamination film and foreign material appearing on a circuit board conducting finger between the electrodes of each electrode pair.

Abstract: A portable calibrator for d.c. circuit breakers is provided which produces a low voltage, short duration current test pulse of a current level sufficient to trip the breaker under test. The current pulse is produced by a high power, high frequency d.c. to d.c. converter which is controlled by lower power signals. A static switch controlled by the converter output provides current protection for the converter. A feedback loop including a current transformer connected in an output transformer circuit provides control of the test pulse. A non-inductive shunt connected in a negative test lead monitors the test pulse during the period of application thereof, the shunt being connected to a sample and hold read-out circuit which includes metering for indicating the peak current value. A timer interlocked with the metering ensures that sufficient time is provided for the operator to read current value.