Can the scan range for RFID tags be set to an exact distance and what is a typical scan time for reading tags.

By range i mean the distance between the reader and the tag. I want to be able to ensure a tag will be found within a certain distance every time. Sort of a proximity sensor with a unique id.

Can the scan range for RFID tags be set to an exact distance and what is a typical scan time for reading tags.
I assume that what you want to do is to sense that the tag is between, say 0.50m and 0.70m from the reader. Well, I doubt that you do that. The reader will sense the tag if it's within the near field. I don't think there's a way to prevent the reader from reading if the tag is too close.





You could put a separate proximity/distance sensor. Ultrasonic, rangefinder, for example.





You could try to judge the distance to the tag by the signal strength of the tag.





Edit: Orientation of the tag has to be always the same to guarantee that the tag will be always read at 0.5m and never read at 0.6m. The object carrying the tag should be always the same too: the reading distance for the same tag on a empty bottle will be different from the case when the bottle has water.





What do you want to do once you detect the distance?





P.S. I will not post to this thread any more. If you want to keep discussing this problem, post to SenSorforum group http://groups.yahoo.com/group/sensorforu... .



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