The invention relates to a system and method for measuring a physical quantity wirelessly, with a emitter and a passive receiver. On the emitter side, the system comprises an RFID emitter in communication with the RFID receiver. On the receiver side, the system comprises an RFID receiver module, energy storage means supplied by the receiver module, a monitoring module for monitoring the stored energy, a microcontroller module with analog-to-digital conversion means, a measurement module, and an enabling module for enabling the microcontroller module. By means of the monitoring module, the system is adapted to taking periodic measurements only when requested, such that even though peak consumptions are relatively high while taking the measurement, mean consumption remains at values that are low enough to supply the measurement module with the energy stored in the energy storage means without requiring any auxiliary energy source.