An RFID sensor system consists of a hardware of a transponder which is known as a “tag” and a reader. The combination of an RFID transponder circuit and sensors which are integrated or are external forms the RFID sensors. Mainly it is used for identification purpose but the combination also enables wireless reading of sensor values and how actuators are integrated.
Battery-free RFID sensors are for passive use that requires energy used for measuring and transmitting and it can be obtained from an electromagnetic field of the reader. An RFID system is completed by the middleware which is the last element and communication can be handled from the transponder to a higher-level system.