UHF RFID Versus UHF RTLS

Many companies new to UHF (Ultra High Frequency) RFID (Radio Frequency Identification) confuse it with UHF RTLS (Real Time Location Systems). While both indeed do use UHF RFID, they differ substantially in what they can actually do for you in your business.

Many companies new to UHF (Ultra High Frequency) RFID (Radio Frequency Identification) confuse it with UHF RTLS (Real Time Location Systems). While both indeed do use UHF RFID, they differ substantially in what they can actually do for you in your business.
UHF RFID

Standard UHF RFID systems can see multiple tags on equipment and products up to several meters away, if set up properly. With emphasis on “set up properly.” While UHF RFID works quite well, its unique characteristics require testing in the environment where it will be used to ensure success.

UHF RFID has several purposes:

    • To see if an item has passed a certain point, commonly known as a choke point. Examples of this are items being loaded on or off a trailer at a shipping door or items passing from one area to another in a plant.
    • To verify if something is within a certain area when using a scanning device, such as a handheld reader. If one is scanning shelves of parts or equipment, it will help locate those items.
    • To track usage of equipment in MIS systems.
    • The tags can also have data written to them if needed.

The big thing that UHF RFID cannot do is effectively track the exact location of something at any given time in a cost-effective manner. Generally, UHF RFID uses what are called passive tags for the antennas to read. These tags have no battery and get energized from the antenna signal. If you placed enough antennas all over a facility and enough of these tags, then you could possibly locate something within a certain proximity, but not exactly, and this is hardly cost effective.

UHF Real Time Location Systems (RTLSs)

RTLS, on the other hand, are specifically designed to pinpoint the location of anything with a tag or transponder on it. In fact, RTLS refers to any system that can accurately determine an item or person’s location. An important aspect of RTLS is how frequently assets must be tracked. This data can be used in different ways depending on the application. For example, some RTLS applications only need timestamps when an asset passes through an area, while others require much higher visibility, requiring constant updating of time data.

An ideal RTLS can accurately locate, track, and manage assets, inventory, or people, and help companies make knowledgeable decisions based on collected location data.

Like regular UHF RFID, RTLS can use passive or active tags (tags with batteries), but they use triangulation of multiple antennas to determine the location of an object or person. The strength of the signal at each antenna, combined with the software attached to the antennas, allows the identification of the location of an object or person within less than 1 meter.

The system you choose depends on the needs at your location. They both work quite well when implemented properly by trained professionals.

Also, due to the inherent properties of ultra-high frequencies used in UHF RFID technology and RTLS, you should perform a feasibility study that actually tests the system in the real world environment of the plant prior to implementing these systems in any application.

Passive RFID Still the Way To Go For Work In Process (WIP)

With the rapid evolution of manufacturing technology it’s pretty tough to keep up with the latest and greatest products designed to help automate the manufacturing process. The big “buzz” surrounding RFID about a decade or so ago was Wal-Mart declaring that their top one hundred vendors would be required to tag every single item with an RFID tag. Well, that never came to fruition. Around the same time there was a lot of talk about active RFID systems as a new technology for work in process. Well, that didn’t ever quite materialize either.

While the active systems certainly have made an impact on yard and container management applications, passive RFID still rules the roost in WIP. In essence, the main difference between passive and active RFID is active tags require a battery which helps tagsto yield a much larger read range. One can imagine the benefits of an extremely long read range in a shipping yard, but on a production line the engineers are just fine with mounting the read head within a few inches of the work pieces. Eighty to ninety percent of the new WIP applications that we deal with still require High Frequency (HF) technology.   The other ten to twenty percent are using Ultra-High Frequency (UHF) which is still passive technology, just a longer read range. This is usually the case where the actual item being built is very large and it is very difficult to place a HF reader within inches of the work piece.

Ultimately, using active RFID for work in process is similar to using a sledge hammer to put a nail in a wall. It is simply overkill. So, while automation technology is on a course of change, it is clear that some of the “old faithful” equipment is still adequately addressing the needs on the production line.

To learn more about active vs. passive RFID tags, click here.