It is a common problem – you are in a bar or restaurant with your drink almost gone and you are desperately hoping that one of the staff will notice and offer you a refill. Sometimes they do, and sometimes they don’t. If they don’t, you leave a little less happy with your experience and are less likely to return, the waiter or waitress gets a lower tip, and the restaurant has lost the chance to sell you a drink. Meanwhile, thirsty customers may stand waiting at the door for lack of a table. Everyone loses. It is such a little thing; yet doing it right or wrong can easily make the difference between economic success or failure.

Since restaurants often make much of their profits on drinks, it is critical for servers to offer refills in a timely fashion. They propose wireless liquid level sensing glassware to aid in this task. Specially instrumented glassware detects fluid levels via a high-resolution capacitance measurement. A coil embedded in the table inductively couples power to the glasses, and provides a path for data exchange. The prototype glass uses a standard microprocessor and a small number of passive components, making it extremely inexpensive.

It is thus critical for servers to offer refills in a timely fashion. We propose wireless level sensing glassware to aid in this task. Ideally, instrumented glassware, or iGlassware, should have the following characteristics:

– Extremely inexpensive

– Washable by standard restaurant dishwashing equipment

– No maintenance issues (e.g. battery replacement)

– Familiar glassware appearance (no wires, not bulky, etc.)

– Support multiple glasses per table

– Globally unique IDs for each glass

– Able to recognize a glass of remaining ice as empty of fluid

– Reasonable measurement resolution.

By using a combination of RFID and capacitance sensing technologies, we are able to achieve these properties.

More here.