FLUID LEVEL SENSOR SYSTEM

摘要

Fluid level sensor. The sensor includes first and second RFID tag antennas disposed in spaced-apart relation on the outside of a container including fluid therein. An RFID reader transmits power to, and receives backscatter power from, the first and second RFID tag antennas. A difference in backscatter power from the first and second tag antennas indicates the presence of fluid behind the second RFID tag antenna. In another aspect, a single RFID tag antenna is disposed on the outside of a container including fluid therein. An RFID reader transmits power over a selected range of frequencies to the tag antenna and receives backscatter power from the tag antenna. The tag response across all frequencies in the selected range indicates no liquid in the container while tag response in only the higher frequencies of the selected range indicates presence of fluid in the container.