Zadeh, mamdani and TSK are proposed different fuzzy conditional inferences for “if ... then ...” to approximate with incomplete information. The Zadeh and mamdani fuzzy conditional inferences are require prior information for consequent part. The TSK fuzzy conditional inference need not know prior information for consequent part but it is difficult to compute. In this paper, new methods are proposed for “if ... then ...” when prior information is not known to consequent part with single fuzzy membership function and two fuzzy membership functions. The two fold fuzzy set made single fuzzy membership function as Fuzzy Certainty Factor(FCF). Sensors are discussed as application for proposed fuzzy conditional inference. Fuzzy inference system (FIS) is discussed for WSN to detect Costal erosion and Turbo Charger Fuzzy Control System as an examples.