The RFID tag I am using is a zip-tie tag. When it is "zipped" up or locked, is there any way for me to see, other than with my own eyes, whether or not my tag is not zip-tied to something? I had expected there to be some sort of indication from the tag itself, or some sort of change within the way it is read once it has been locked (that is, once it has been attached to something). Is this possible?
Some passive UHF RFID transponder chips and some passive HF RFID chips have an I2C interface that allows you to send data to and from a chip. You could, for example, connect a temperature sensor that would transmit the temperature of the environment in which the tag was sitting to the chip, then store that data in user memory. When the tag was read, the temperature would be transmitted to the reader, and then on to a back-end system.
To determine whether a bag, box, or other object was in an open or closed state, you would need some kind of sensor or electrical switch that would determine that state, then link that information to the chip via the I2C interface. Your reader would need to be set up to read the tag data and report it to your software application. I hope this answers your question.
—Mark Roberti, Founder and Editor, RFID Journal
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