• What would be the best type of RF tag—active, passive or semi-passive?
• Which type of reader would be suitable for this application?
• Can you offer a rough estimate regarding the price of RFID tags and readers?
Thanks in advance!
There are several ways in which you could handle this application. Perhaps the easiest would be to have a short-range high-frequency (HF) ID card that each worker would swipe in order to enter and leave the building; you could use different doors, so that you would know who is entering and who is leaving. The card would be read instantly when tapped on a reader near one of the doors, so it should not cause any lines to form.
If you are seeking a way to automatically identify an employee and determine whether he or she is entering or leaving, then you could utilize a passive ultrahigh-frequency (UHF) transponder. There is often a challenge reading UHF tags close to a human body, however, because the body’s water content can absorb a reader’s energy, thereby preventing a tag from using that energy to reflect back a signal to the interrogator. If workers wear a helmet, that would be a good place to situate the tag.
Another issue is that a worker could hide the tag under his or her arm in order to avoid being detected. This could be a problem if you are concerned about employees leaving during the day and returning later on, and then claiming they were working the whole time.
An active, real-time location system (RTLS) could determine where workers are located at all times. This could solve your problem—but your staff might not like having their movements monitored. Another issue involves your facility’s physical layout. If there are a lot of small rooms and corridors within your building, it could prove challenging to cover the entire area.
So the proper solution really depends on a variety of factors: layout, whether workers need to be identified automatically, and whether you are concerned about employees sneaking into and out of your facilities.
As far as price goes, ID cards with HF transponders will cost approximately $1 apiece, while the two readers will cost $300 to $400 each, plus the expense of installation and integration with attendance software. A label with an embedded UHF transponder would be cheaper. This would only work if you can stick it onto a helmet or something else worn by a worker.
If you need to create UHF badges, that will likely cost $1 or so apiece. UHF readers are priced at around $1,000 each, plus installation and integration. An active RFID-based RTLS would be considerably more expensive. For one thing, the tags cost $25 apiece or more. You would also need to install readers around your facility, in order to interrogate the tags, and you would require an application to pinpoint a tag on a map of your facilities.
I hope this information helps you.
—Mark Roberti, Founder and Editor, RFID Journal
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