Getting an accurate inventory count is one of the most important tasks in an organization because so many other business functions depend on it. Even small errors in the count can have a big impact down the line, leading to problems in purchasing, shipping and receiving, tracking, warehousing, storage, turnover and reordering. If decisions are made based on faulty inventory counts, you can create serious issues in supply chain management, production control, financial flexibility and customer satisfaction.
That’s why many organizations use RAIN RFID technology to know what’s on hand. Inventory control systems that use RAIN RFID tags to identify and count items often deliver faster, more accurate results than those based on methods such as manual counts or bar codes.
RAIN RFID tags are inexpensive to produce and easy to deploy, since they operate on a global standard that can be used all over the world. The tags themselves are flexible and suitable for use with a very wide range of items, ranging from raw materials to finished goods and even livestock. RAIN RFID tags also make it possible to count large batches of items at once (as many as 1,000 tags can be read per second, without line of sight, with accuracy ratings in the high nineties). Many deployments achieve accuracy rates approaching 100% across the solution.
There are, however, a few factors that can affect accuracy. To begin with, some tags are better than others at responding to reader signals. Variations in manufacturing quality and antenna design can create tags that are less sensitive to RF signals, making it harder for the tag to respond to signals coming from the reader.
The operating environment can have an impact, too. The tag’s orientation can limit its ability to receive and respond to the reader’s signal and the reader signal itself, which carries the power used by the tag to respond, can become too weak to trigger a response if it passes through material that is too dense before reaching the tag.
Tags that are less sensitive to RF signals, either due to their own limitations or because of their positioning or environment, may not be able to power up and respond and as a result may be missed. The good news is that the RAIN RFID standard includes a special mechanism, called a session, that makes it easier to deal with these variations in tag strength, especially when tags are crowded together in large groups, such as when they’re packed into a container, piled onto a pallet or displayed in a densely populated retail store.
The session mechanism can help prevent stronger tags from repeatedly overshadowing weaker ones. Once a given tag has reported its identity, by returning the EPC number to the reader, it goes dormant. The tag stops responding and consuming the airways so other tags in the group can make their replies. Stronger tags are likely to respond first, so silencing them once they’ve responded gives weaker tags a better chance of being heard.
The session mechanism also helps multiple readers operate in the same area without interfering with one another or interrupting counts. Since so many of today’s RAIN RFID applications include a mix of portal gateways, overhead systems and handheld readers, the sessions can help maximise accuracy in what would otherwise be a difficult environment for achieving accurate reads.
From a design standpoint, making good use of RAIN RFID sessions is essential to ensure hardware and software components involved in inventory control can work together effectively and produce highly accurate results.
Our new white paper, titled “Mastering the Art of Inventory Control”, introduces the session concept. It explains how RAIN RFID sessions work, identifies the different type of sessions and gives two real-world examples (a retail outlet and a supply cabinet) to describe how sessions can increase accuracy.