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Smartrac's New Passive Sensor DogBone Transmits Moisture Levels

The company has begun shipping the UHF tag to systems integrators to begin proof-of-concepts and the development of applications in the manufacturing, health-care and agriculture sectors.
By Claire Swedberg

Although Strömberg declines to provide names or specific descriptions of the pilots underway during the past year, he says several of the pilots were testing the tag for measuring moisture presence in containers. At least one pilot participant was also in the health-care market, though he says he cannot describe how that firm is testing the Sensor DogBone.

Strömberg envisions the tags being used in a variety of other ways as well. The Sensor DogBone can identify moisture presence in a material, such as wet soil or concrete, and future versions of the tag are expected to be able to sense moisture in ambient air. For that reason, the tag could inform users, via an RFID reader, regarding the moisture level in a room or cooler, as well as in construction materials for which moisture must remain at a very specific level. It could also be used in the agriculture industry, to measure moisture levels in soil.

The tag is designed to work with a variety of low- or high-dielectric materials, including wood, cardboard, plastic, stone or construction materials.

Just like Smartrac's standard (non-sensing) DogBone tags, the Sensor DogBone's die-cut size is 97 millimeters by 27 millimeters (3.8 inches by 1.1 inches) and its antenna measures 88 millimeters by 24 millimeters (3.5 inches by 0.9 inch), though the antenna shape is more complex than that of Smartrac's non-sensor DogBone tags. The Sensor DogBone, which ranges from 200 to 300 microns (0.008 to 0.01 inch) in thickness, comes with 64 bits of tag ID (TID) memory, 128 bits of Electronic Product Code (EPC) memory and 144 bits of user memory. Strömberg says the read range is similar to that of a standard UHF DogBone tag.

Because the tag requires a reader to transmit sensor data, it cannot behave as a data logger, and users would thus need to capture periodic reads if they wanted to collect a history of measurements. However, he says, this process would work well for those who wanted to store information on a cloud-based server, since a reader could automatically forward sensor measurements to a server each time a tag was read, thereby creating an electronic record. Because the Sensor DogBone is totally passive, he adds, the company has enabled the tag to be embedded, for example, within a building's structural material—an application that would be impractical for a sensor with batteries that had to be replaced.

Smartrac expects systems integrators to develop solutions for the tag that the technology developers had not even considered. "Time will tell where this goes," Strömberg says, "but it's going to be an interesting ride" as developers create solutions using the tag. Traditionally, he notes, in developing the best RFID tag in terms of transmission reliability and range, Smartrac focused on tuning an antenna according to the materials that the company expects will be in the tag's vicinity. Now, the firm is taking a new approach by using an IC that tunes itself based on the antenna's impedance. "We are climbing our own learning curve now as we have added this new dimension."

According to Strömberg, the Sensor DogBone tag costs about 50 cents apiece.

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