Water Purifier Relies on RFID for Safe Operation

According to Baarman, RFID proved to be the best means by which to convey data between the lamp and filter and the main control unit, because the system's design does not allow for a direct line of sight—ruling out infrared or bar-code solutions to identify the lamp and filter—and since communication must be wireless. Fulton experimented with a number of higher-frequency RFID tags and readers, but the fact that the filter and lamp are surrounded by water moving through the system meant only low-frequency technology could perform with consistent accuracy. (Water tends to interfere with RF signals at high frequencies.)

The tags play two main roles, Baarman explains: They allow the main control unit to identify the lamp and filter, and they also provide a means of associating the usage data with a specific filter and lamp, so that this data can be regularly updated and the control unit can alert the user when either the lamp or filter has reached the end of its safe operating life and should thus be replaced.

Because the lamps and filters are manufactured in different countries, and since the exact powering specifications can vary between nations, the tags attached to the lamp and filter contain operating instructions that are conveyed to the interrogator through the tag data. The reader then conveys these operating instructions to the main control unit.

When the system is in use, one sensor measures water flow, while another tracks the lamp's power cycles. The RFID reader periodically writes this data to the tags on the filter and lamp. Later, when the reader interrogates the tags, it transmits this information back to the main control unit. Once the lamp or filter has reached the end of its useful life, the main control unit emits an audible warning and a visual alert on a small LED display.

Alticor has sold more than 1.5 million eSpring units to date, in more than 36 countries worldwide. Demand for the water-purification system is especially strong in Asia, Baarman notes, where municipal water quality is less consistent than in the United States.