Detection is a basic way for people to know the objective world and gain qualitative and quantitative information, which has been an indispensable component of modern technology. Detecting technique is a vital measure of technological experiments and manufacturing process. It can reveal the internal relationship, develop laws and then utilize them to promote the development of detection.

The development of the society and science makes higher requirements of detection technology. In actual application, information detection technology is developing with computer technology and micro-electronics technology. However, some information is immeasurable in some circumstances,

Conventional detecting technique achieves the detection of the target by enhancing the research of sensors. For the inscrutable thing, it is hard to go a step. Even the estimation of detecting outcome by some mathematics calculation is not ideal. Extension detection emerges to solve contradictory problems occurred in industry, agriculture, national defense and administration aspects resulting from inscrutable problems.

Researching objects of Extenics are contradictory problems. Both matter element theory and extension set theory support Extenics in theory. Extenics founds formalization method and describes contradictory problems of objective world. It applies extension transform method to transform contradictory problems. And it is a breakthrough of the weakness that conventional mathematics can only solve precise problem. For contradictory problems, it applies qualitative and quantitative analysis. What is more, it fits the developing law of objective things. Extension detection combines the characteristics of Extenics in favor of solving contradictions, applying divergent creative thinking and multiple ways like extension transformation, goodness evaluation, and extension reasoning of Extenics, seeking solution of detecting and enhancing precision from new angle. Extensive detecting technology studies the conformation of detecting strategy and explores inscrutable and scrutable matter elements converting principle by extension reasoning, avoiding the aimlessness and uncertainness of detecting. And then a set of advanced detecting theories that differ from conventional methods is established.

The technology of extension detection is created for tackling immeasurable problems with a combination of Extenics and detection technologies. It has tactfully applied the method and theory of contradiction analysis in Extenics and combines the relatively mature sensor technology at present to convert the immeasurable problems into measurable ones.
Professor Yu Yongquan puts forward the concept of extension detection, basic principles and related achieving methods. Furthermore, he proved the feasibility of extension detecting technology by some practical application. Extension detection is developing rapidly. Its system frame has been established, which can advance the detecting techniques and methods for inscrutable physics research of the system in specific conditions. Extension detection has already made some interrelated achievements, and provided new thinking for the detecting problems in industrial manufacture and national economy.

The main research contents of extension detection cover extraction of fundamental material elements, adaptability analysis, focus and knowledge inference mechanism generation, focus revealing. In the extension detection, at first, a material element analysis is conducted on the detected object and divide the object into measurable and immeasurable elements; the detection on immeasurable material elements is realized through that conducted on measurable material elements in which the status of immeasurable elements is figured out by making a material element conversion on the results of measurable element detection so as to get the detection results from those material elements which are immeasurable originally.

Extension detection studies how to solve the problems that are unable to detect when there are no sensors to enhance the accuracy of detection results. The technology is innovative, extensive and scientific, blazing a trail for the development of detection technologies.