A circuit, method, and system including the circuit such that the circuit is for a passive radio-identification tag operating in a UHF band and is configured for radio communication with a reader which sends a periodic read signal. A period of the read signal includes an energy recovery phase and a communication phase. The circuit has: a control device configured to accumulate an energy reserve from the radio wave during the energy recovery phase and to communicate with the reader during the communication phase, an interface to connect an external analog sensor. The interface includes: an electrical connection configured to connect and supply the external analog sensor with electricity and to acquire the analog measurement from the sensor, an amplifier configured to amplify the signal of the analog measurement from the sensor, and an analog-digital converter configured to digitize the amplified analog measurement from the sensor.