The testo 115i Smart Probe is a pipe-clamp probe that measures temperature in pipes more accurately than thermocouples because of the superior NTC temperature sensor technology. The exclusive Testo probe design grips pipes up to 1. 5″ and maintains critical contact between probe and pipe surface to derive the best readings. Users can read the measurements using the testo Smart Probes App installed on their smart device. The testo 115i works on smart devices with either Android or Apple operating systems at distances up to 350′.