measuring apparatus for measuring the quality and quantity of electricity and its properties; measuring devices, electric, namely, electric sensors; electric measuring devices, namely, sensors for measuring alternating current (AC), direct current (DC), direct current (DC) leakage, alternating current (AC) and direct current (DC) Hall effect, voltage, and energy; surveying apparatus and instruments; electrical inductors; coils, electric; electromagnetic coils; variometers; electrical transduc...