In this study, we developed a portable X/gamma-ray survey meter for large-scale distributed real-time monitoring of the ambient dose equivalent rate in the surrounding environment, using a silicon photomultiplier coupled with a CsI(Tl) scintillator. This innovation is integrated into an Internet of Things (IoT) network. The device realizes a wide range of dose rate measurements by switching the frequency of a pulse-frequency modulation (PFM) -type DC-DC power supply mode. The energy response is improved through Geant4 simulation and multicomparator design.