Abstract: A pair of relatively movable, shrouded jaws are provided for a hook-on type measuring instrument to insulate the conductive ends of the jaws from contact with high voltage electrical conductors on which the instrument is periodically clamped during its normal application. The shrouded ends of the jaws are characterized by incorporating cup-shaped insulated recesses within which the uninsulated ends of the soft iron magnetic ends of the jaws are disposed substantially below the outwardly extending lips of the recesses thereby to prevent the iron from being inadvertently placed in contact with a high voltage conductor when the jaws are opened to either place them around such a conductor or to remove them therefrom.

Abstract: An instrument having an indicating scale and a pointer movable in relation thereto is provided with a pointer clamping mechanism having a bistable retainer that cooperates with a manually operable actuating member to selectively retain the clamping member in either its pointer-clamping position or in a stored position after it is moved to one of such positions by the actuating member. Positive movement of the clamping member between its two positions is achieved by a connector fastened directly to the clamping member and coupled to the actuating member in a manner that causes the connector to be resiliently loaded when the clamping member is moved away from its stored position.

Abstract: A probe assembly for use with an electrical voltmeter-ammeter, to adapt the meter to read electrical resistance, is provided with a pair of probe electrodes connected respectively to separate, flexible, insulated electrical conductors that are coupled to a common multi-terminal plug housing. Terminals mounted in the plug housing are arranged to cooperate with a plurality of terminals mounted on a terminal board in a meter. The probe assembly is further characterized by incorporating a fuse and a battery electrically connected in series with one of the probe electrodes and the terminal to which it is connected by a flexible conductor. A potentiometer is connected in series with one of the flexible conductors while a resistor connected between the flexible conductors to enable a meter to be adjusted for full scale deflection when it is connected to the probe assembly while the probe electrodes are in engagement with one another.