RFID tag antenna based sensing: Does your beverage glass need a refill?

Liquid level detection in customer beverage glasses and liquor bottles in the service industry is important for maintaining quality of service and good approval ratings. Current sensing approaches rely either on visual inspection or expensive sensor electronics to detect liquid levels. In this study, we investigate how the paradigm of RFID tag antenna based sensing can be used as a low-cost alternative in the service industry, to detect the volume of liquid in a beverage glass by mapping a change in RSSI power measurements from RFID tags to the level of liquid in the glass. We demonstrate that this sensing technique when deployed in a real restaurant-like setting can be used to accurately predict the state of the glass over 80% of the time, and thus has good potential as a low-cost sensing methodology for applications in the restaurant industry.