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.

Add Transparency and Traceability with RFID

How can traceability and easy data collection help make the assembly line more transparent and efficient? I’m sure if you ask any manufacturing engineer if being able to track vendor and lot information is going to benefit them in some way, they are going to say yes! All companies have some type of ERP system set up to track parts coming in and products going out, but what goes on between those lines? If a customer reports a missing or faulty component how do you easily know where it came from?  How do you know when the product was made or who made it?

This is where RFID comes in. RFID read/write heads and data collectors can help you track and control production on the assembly. These data collectors or “tags” come in various shapes and sizes. They can be small chips attached to the workpiece carrier or they can even come as a bolt that you screw right into your part. Read/write heads also come in different sizes and have variable read/write distances or frequencies (i.e. low frequency, high frequency, and ultra-high frequency). The read/write heads connect to a processor unit that ties directly back to the PLC. Once the PLC receives this information, it can provide it to the ERP system. This takes all the information on the floor level and makes it available to the management system.

For example, say you have an unexperienced line worker on your assembly line. You are producing large diesel engines and he has the job to put together the pistons at the front of the line. Many times, he snaps the O-rings putting them on. Other times, the rings aren’t put completely in place, but he still sends the engine to the next station. When customers start calling faulty O-rings, you need an easy way to locate the source of the problem.

If you have 10 different lines changing out various engines every day, it could be difficult to narrow down the source of the problem. But if you have RFID read/write heads at each station on the line and a tag on each engine, you can look into your ERP system and track down on which line the engines in question were assembled and who was responsible for putting together the pistons.

You can then determine if the problem was human error or if the cause was due to poor quality parts, and take steps to rectify the situation. If it is determined that the rings are poor quality, you can easily determine every engine that these rings have been used on and recall only those engines. This is just a small example of how RFID can help with transparency on the assembly line. If you are looking for better ways to track inventory, vendors, or just make data more accessible to you and your company, then RFID is your answer!

What to Ask Before You Build an RFID System to Meet Your Traceability Needs

An industrial RFID system is a powerful solution for reliably and comprehensively documenting individual working steps in manufacturing environments. But an industrial RFID system that meets your application needs isn’t available off-the-shelf. To build the system you need, it is important to consider what problems you hope RFID will solve and what return on investments you hope to see.

RFID can deliver many benefits, including process visibility and providing data needed to better manage product quality. It can be used to improve safety, satisfaction and profit margins. It can even be used to help comply with regulatory standards or to manage product recalls. And RFID can be used in a wide range of applications from broad areas like supply management to inventory tracking to more specific applications. These improvements can improve time, cost or performance—though not typically all three.

It is essential to understand and document the goal and how improvements will be measured to in order to plan a RFID system (readers, antennas, tags, cables) to best meet those goals.

Other important questions to consider:

Will the system be centralized or de-centralized? Will the system be license plate only or contain process data on the tag?

How will the data on the tags be used?  Will the information be used to interface with a PLC, database or ERP? Will it be used to provide MES or logical functionality? Or to provide data to an HMI or web browser/cloud interface?

Will the system be required to comply with any international regulations or standards? If so, which ones: EPC Global, Class 1 Gen 2 (UHF only), ISO 15693, or 14443 (HF only)?

What environment does the system need to perform in? Will it be used indoor or outdoor? Will it be exposed to liquids (cleaning fluids, coolants, machine oils, caustics) or high or low temperatures?

Does the RFID system need to work with barcodes or any other human readable information?

What are the performance expectations for the components? What is the read/write range distance from head to tag? What is the station cycle timing? Is the tag metal-mounted? Does the tag need to be reused or be disposable? What communication bus is required?

With a clear set of objectives and goals, the mechanical and physical requirements discovered by answering the questions above, and guidance from an expert, a RFID system can be configured that meets your needs and delivers a strong return on investment.