Optimizing Performance of UHF RFID

In manufacturing and warehousing EPC Gen2 tags have become the standard. These Ultra High Frequency or UHF tags are a good choice for these environments for a number of reasons:  

  • EPC Gen2 provides a wide variety of read ranges   
  • EPC Gen2 can be encoded and printed on a standard RFID equipped printer
  • EPC Gen2 is relatively inexpensive

Optimizing UHF Tag Performance

A number of factors affect tag performance, especially in these environments. But as long as you know what to look for and plan accordingly, RFID delivers many benefits.  

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Tag Size and Read Distance

Tag size and read distance are directly related.  Generally speaking, the size of the tag affects the size of the antenna which in turn affects read distance. So identifying tag size and desired read distance at the onset of the project is a must.

The reader and number of antennas attached to the reader can enhance signal strength/read distance, but only to a certain extent. Doing the math upfront is an important piece of the puzzle to ensure optimum performance of your RFID system.

Environment

Environment is a very important factor to consider in tag selection. Both the general environment in which the tag resides, as well as the item being tagged; both its surface and where applicable what’s inside the item being tagged, are all factors that need to be taken into consideration in tag selection.

General Environment 

Manufacturing and DCs can be tricky environments for RFID use. In manufacturing, electrical noise from machinery, lighting and the like can interfere with RFID signals. In warehouse environments, metal surfaces (shelving, metal items, machinery, etc.) can affect the RFID signal, as can the density of the product on the shelves and the continually shifting configuration of any warehouse. Testing is always the answer to making the right choice and should be as close to what you anticipate real conditions will be (labels, reader, label placement, antenna placement etc.) to get the most accurate results. 
 

What’s Being Tagged

There’s very little that can’t be tagged, but some surfaces are harder to tag then others. Tagging metals can be problematic as metal reflects the signal and can short out the antenna. A layer of insulation between the tag and metal surface is the remedy. There are tags specifically made to be put on metal surfaces. However, the Zebra Silverline product is the only RFID tag for metal surfaces that can be printed on demand.   

What’s Inside What’s Being Tagged

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Liquids are known for being troublesome for RFID, as they can absorb the RFID signal. However, not all liquids are created equal when it comes to their difficulty factor. Take water and oil for example: they are at opposite ends of the scale . . . water having little to no effect on tag performance and oil being one of the most difficult substances to tag.  So what’s the difference?  It’s the amount of carbon in oil that affects RFID performance.  So if you’re talking salad dressing you’re okay, but motor oil (or any other carbon laden substance) that's another story.     

Tag Density

When mapping out your RFID strategy, the tag density or number of tags in a given area, should be part of the conversation. For example: When a large number of small,  individually tagged items are put in a larger container, it might be difficult to make sure each tag has been read. In cases like this, we recommend content is known in the supporting data.

Tag placement 

Where a tag is placed is also an important factor to consider. When tagging on the outside of an object, uniform placement is typically the best practice.  However, there are exceptions to this rule. Take for example cartons that are being palletized.  Depending on the carton size and/or the size of the pallet, cartons may not all be stacked in the same direction and could contain inner cartons. 

In many manufacturing use cases, the RFID tag is placed on the inside of an object or its packaging. This is especially true in automotive and aerospace manufacturing where suppliers have a requirement to track sub-assemblies and placing the tag on the outside of the part is not an option. The material and density of the object will affect the performance of the tag, so testing is always recommended.

Other factors including tag size, reader strength and tag density will also figure into the equation when determining tag placement.

Test, test, test! It's all about fine tuning the solution for optimum performance.