Shaanxi SK electronic technology company is a high-tech enterprises, Located in Xi `an high-tech industrial development zone.SK rely on xi `an universities of science and technology resources, committed to liquid level instrument’s research and development for petroleum, chemical industry, pharmacy, electricity, metallurgy, military industry, storage Etc. SK Company dives in the study of Sonar technology, actively explore the technology and apply it to the industry automation control field. Three new products have been widely used in kinds of market, the two-wire non-intrusive ultrasonic level gauge, the four-wire non-intrusive ultrasonic level gauge and non-intrusive ultrasonic level switch. All these three products’ capability has reached the international standard. Especially the two-wire external liquid level indicator is the first type in the world.