Abstract: A differential electrical current shunt which is particularly adapted for the measurement of large currents with high accuracy and substantially free of errors due to ageing, connection resistance and differentials therein and thermally induced resistance changes. The shunt, according to the invention divides the large current into two substantially equal portions by forming a preferably elongated aperture in a conductor carrying the large current; the two portions of the conductor formed by the aperture having substantially equal but slightly differing resistances. The two conductor portions are formed with respect to a core such that the conductor portions each form a single turn coil on the core with the induced flux from each conductor portion opposing that included in the coil by the other of the two conductor portions.

Abstract: An apparatus for indicating the peak tangential velocity of a swung sporting goods implement such as a tennis racquet, golf club, or baseball bat, comprises a tube having a longitudinal bore. A seismic mass is slideably disposed within the bore of the tube, and a spring operates to pull the seismic mass toward the proximal end of the tube. A reset mass is normally captured at the distal end of the tube but is selectively released to slide within the bore of the tube. A peak velocity indicator is slideably disposed within the bore of the tube between the seismic mass and the reset mass, the peak velocity indicator frictionally engaging the inner walls of the tube such that it is displaceable longitudinally within the bore of the tube by an applied force but maintains its position within the bore of the tube once the applied force is removed.