An improved sprinkler includes a spray nozzle, an adjusting sleeve, a barrel set and a hose connector. The protective layer comprises a microencapsulated diarylethene material that is capable of switching between a UV absorbing and UV transparent state. A calculator groups the measurement information by target on the basis of signal intensities and phases of the reflected electric waves in different frequency bands, and calculates the position of the target with respect to the longitudinal direction of the leaky cables and the distance between the target and the leaky cables.