As RFID supplants bar codes across the supply chain, SIMATIC RF600 UHF-based solutions provide dramatic reductions in programming complexity.
In business it’s sometimes said, “you can’t manage what you can’t measure.” That’s why process visibility is so vital to process control and asset utilization in the world’s factories and, by extension, why it’s a key to improving their production efficiency and ultimately their profitability. The same holds true for the world’s supply chains that move feeder stocks and finished goods.
RFID is taking over this field, partially because it doesn’t need line-of-sight to read tags like bar codes, an optical technology. Radio tags can be embedded in goods, on cases, or on pallets. The technology can also provide much more information than bar codes, up to 4KB with UHF tags.
One key advance was the introduction of the EPCglobal Class 1 Gen 2 standard, which provides for RFID using the UHF radio spectrum, 901-928 MHz in North America and 865-868 MHz in Europe. This article explains ultra high-frequency (UHF) RFID technology and how it differs from – and can complement – its cousin, the widely deployed high-frequency (HF) RFID technology.
RFID technology has helped companies worldwide drive out huge amounts of variability and errors as well as time and costs. It has given them much greater operational visibility and asset utilization. They’ve achieved levels of traceability that weren’t possible before. All this has helped them to realize huge improvements in speed, quality and profitability.
A key point: UHF is not “better” than HF or LF; it just provides more options and capabilities to extend the already broad range of RFID applications. Successfully implementing an RFID system – whether HF or UHF — often requires a large investment of money, time, and effort, but the potential value of a carefully planned RFID-based system will far outweigh its costs. Here are some steps that can help ensure a successful RFID implementation.
Programming and Integration
This important step ties the UHF RFID system into the intelligence of any PLC or PC-based manufacturing control systems through their associated automation networks. OLE for Process Control (OPC) servers can be subsequently utilized for host system integration.
Significantly, the PLCs can use the RFID monitoring data for production decisions about work-in-progress, such as ascertaining that the needed number of red-painted items is met and directing machinery to paint the next 10,000 items blue.
A UHF RFID system can also communicate tag data with higher-level, PC-based manufacturing execution systems (MES) and enterprise resource planning (ERP) systems. The data can be used by those systems any number of ways, like building or adding to a database record that logs the provenance of an item or a case or pallet of items. Another example would be to order more feedstock inventory.
Site Assessment and RF Engineering
A thorough site assessment should achieve the following: define the context of where the RFID solution will be deployed; gather information needed to specify the solution’s implementation requirements; and predict the performance of the solution against those requirements.
Most of all, it’s important to survey a site’s existing RF environment. That’s because interference from wireless networks as well as from other sources like short-range radios, cordless phones and motors can degrade RFID system performance.
The reflectivity of metal fixtures and shelving can affect RF engineering, too. The reflective impact of metal on the UHF RF fields is critical.
Note that with a radiating and receiving distance of up to 26 feet (8 meters), UHF provides both near-field and far-field read capabilities. While the former operates similarly to HF RFID, the latter’s 70-degree field quickly expands the potential for RF interference the greater the distance from the UHF antenna. That’s why much consideration must be given to the absorptive, refractive and reflective properties of the surroundings.
The absorptive impact of liquid also has significant impact on the UHF RF fields. There can be shadows behind the liquid’s container, and energy is diminished in the main RF field surrounding the container. Also keep in mind the human body is approximately 65 percent water, so workers in the RF fields have absorptive impacts that RF engineering must address.
The good news is that all these various RF impacts can often be mitigated by using multiple antennas and “right sizing” RF power in UHF RFID read zones, for example with the Siemens RF600 family of readers.
Those mitigations can then be extended by optimizing the angle of the antenna to maximize the “reply” signal strength of the tags (i.e., transponders), which is measured by a value known as the Received Signal Strength Indicator (RSSI).
In SIMATIC RF600 readers, UHF algorithms including RSSI Threshold and RSSI Delta can be employed to automatically adjust a reader’s sensitivity to tag signal strength. The software has a graphical interface to easily monitor the RSSI value of readers’ antennas in real-time as their angles are adjusted. This saves a lot of time in the actual installation, fine-tuning and ultimate commissioning of the readers. What’s more, the RF600 software can automatically right-size the RF field in steps to minimize overshoots using a UHF algorithm called the Inventory Power Ramp.
Conclusion: As a welcome complement to HF-based RFID, UHF-based RFID solutions can provide longer reading ranges, faster reading speeds, and much more simultaneous tag-reading capacity. These capabilities can enable manufacturing and logistics operations to expand RFID’s use and provide even greater visibility and control of their processes and assets.
Like any industrial application, RFID requires careful planning, engineering and execution. UHF RFID can pose particular deployment challenges, especially in RF engineering. Issues of RF absorption by liquids, reflectivity by metals and interference from other RF energy sources must be addressed.
If companies lack in-house RF engineering expertise, there’s plenty of help available, especially from highly qualified Siemens Solution Partners. In addition, advanced UHF RFID components such as those in the Siemens SIMATIC RF600 product family can dramatically reduce programming chores and RF guesswork.
With proper planning, a successful UHF RFID deployment can provide many years of profitable returns to manufacturing and logistics operations.Have an Inquiry for Siemens about this article? Click Here >>