01-05

RFID is becoming more mainstream thanks to mandates from Wal-Mart, DoD, Target etc… now would be a good time to go over some RFID basics and challenges that confront new RFID implementations and emphasize the importance of certification and a site survey. I’m going to limit this discussion to EPC Global standard tags-Class 0 and Class 1.

Basic RFID tags are really just barcodes that can be read without being seen. That is, they’re not line-of-site. You don’t have to actually see it to read it like you do a barcode. A basic EPC Global Class 0 tag has 96 bits of “memory”. It can hold a single 8 character (8 bits per character) hex number. A Class 1 tag can be either 64 bits or can hold slightly more, up to 96 bits (12 characters).

The difference between Class 0 and Class 1 tags is the ability to erase and reprogram the tag. A Class 0 tag comes preprogrammed from the factory and cannot be erased or modified. A Class 1 tag can be erased and reprogrammed. There is a new tag standard in the works known as Gen2, which will hold more data as well as being reprogrammable and can support a multitude of data logging functions.

The EPC Global organization (Electronic Product Code) is an industry driven organization chartered with developing standards for RFID. The standards currently active are the Class 0 and Class 1 RFID tags with Gen2 soon to be ratified.

EPC Global Class 0 and Class 1 (Which I’ll now refer to as Class 0 and Class 1) are designed to work in the unlicensed 900 Mhz ISM band. 900 mhz is a frequency band that provides a good balance of antenna size and read distance as well as almost world-wide availability.

The challenges to EPC based RFID implementations from an RF standpoint are very similar to the legacy generation of 900 Mhz Wireless Data Collection networks. A site survey of the facility is crucial. Even though an RFID system doesn’t have the coverage of a Data Collection network, it has many of the same issues. Some of these are:

1. Interference from other 900 Mhz devices such as cordless phones.
2. Multi-path interference from metallic objects.
3. Absorption of the signal by objects with high moisture content.
4. Antenna orientation in relationship to tag presentation.
5. Tag read distance from Antenna

A site survey of the area where tags will be read will determine where antennas need to be placed, as well as that quantity and antenna type.

One of the most critical things to know is what object is to be tagged. Cases? Pallets? Individual items? Tag selection and placement is almost an art as it is a science. What is the pallet made of? Tags behave differently on oak pallets vs. pine pallets. Some are plastic and even though they may be easy to tag, would you want to tag a pallet that you don’t own and have to return?

The two biggest challenges to tag placement are metal and water. Water absorbs RF. A tag placed on a bottle of baby shampoo or large jug of laundry soap will virtually kill the RF signal. But a tag placed on a bottle of baby oil will read just fine, even through the product. Dishwasher detergent boxes are partially made with shiny foil, and the metal kills the RF signal. Some black plastic containers and anti-static carriers for circuit boards have high carbon content that complicate a proper read.

Can these problems be resolved? In many cases yes through creative tag placement and special tags designed for these hard to tag situations. Be advised: You may find that there are some items that just can’t be tagged.

Another thing you have to ask yourself during your planning phase is how will the tag be presented to the antenna? Most RFID readers support two types of antennas: Linear and circular. Linear antennas read in one polarity, either horizontal or vertical depending on how the antenna is oriented. The tags must be presented in exactly the same orientation or it won’t be read. These kinds of antennas however have the best-read distance. This can be several feet or more depending on the product being tagged. Circular antennas are much more forgiving. They can read a tag in almost any orientation except perpendicular. However, these antennas have about half the read distance of a linear. Once again, know how the tag will be presented to the antenna: on a pallet where everything is one way or various ways? On a conveyor where products could be on their side, or upside down? Will the conveyor need to be modified to allow the installation of an antenna?

Next question: how will the tags be placed on the product? What if the best tag placement happens to be right over the product label or serial number label? Will a packaging engineer need to be brought in to possibly redesign the labeling to make room for the tag?

What does all this have to do with site surveys? Part of the site survey process is to gather information on the customer’s processes. A site survey allows you to visit the site and see these things for yourself, and a properly planned and implemented RFID installation will prove to increase your bottom line and your customer’s productivity/business flow. WAV is RFID certified and has a team of technicians that specifically handle site surveys.

I’ve only just touched on a few of the many “gotchas” of RFID implementation. In order to succeed, training and certification from the RFID vendor is critical, and will guide you through many of the challenges mentioned above. You will find that certification and site surveys are mandatory from most RFID vendors.

Careful planning and consultation with your RFID vendor and the customer will go along way towards a successful implementation. Remember to do your homework!