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Metal-Powder Factory Adopts IRID

To help it track production, a Swedish maker of metal powders switched from RFID to an infrared auto-ID system.
By Rhea Wessel
Aug 23, 2007Höganäs AB, a Swedish producer of metal powders used to make engines, drive systems and tools, is using a infrared auto-identification system to track containers filled with metal powders at its factory in the city of Höganäs. Instead of transmitting data by means of radio waves, as RFID systems do, IRID tags and readers transmit using infrared signals. Swedish passive infrared identification system developer Scirocco provided the system, dubbed IRID for infrared identification (see Sound and Light).

To better control its production process, Höganäs had wanted an overview of which metal powders are at what stages of production. It had been using an RFID system to identify containers, but it faced several problems with RFID. For instance, Höganäs was using a system with a low read range because that was what was available at the time of installation many years ago. Occasionally drivers miscalculated and ran their trucks into readers, and replacing the parts was difficult. In addition, the metal environment of the factory caused RF interference—that is, it was hard to set the tags at the right distance from readers.

The IRID tags are about the size of a credit card.
When Höganäs decided to replace its older RFID system, it considered an RFID platform with a longer read range, as well as bar code technology. It decided against longer-range RFID system because of the risk that an interrogator would capture data from the wrong tag and that multiple interrogators might interfere with one another. Moreover, the price of the RFID system was high in comparison to the 50,000-euro IRID system, which included readers, tags, programmable logic controllers (PLCs) and software. (The PLCs are installed next to the readers and serve several purposes, such as handling the interface with other equipment and visually indicating a container's ID number.) Höganäs dropped the idea of a bar code system because it feared that airborne metal dust in the factory would quickly coat the bar code labels, making them illegible. Höganäs' own tests before ordering the system from Scirocco showed that IRID signals, with have a wavelength twice as long as that of visible light, penetrate the metal dust on tags and interrogators without significantly reducing the read range.

Scirocco's interrogators and tags contain light emitting diodes (LEDs) to generate the IR signals, and photovoltaic cells to receive them. The tags, which can be read and encoded by an interrogator up to 3 meters away, have no battery and are instead powered by an interrogator's infrared signal. Since infrared waves have controlled propagation characteristics, explains Staffan Sjögren, Scirocco's managing director, the system's read/write zone has no dead spots and the zone's outer borders are sharply defined, reducing the likelihood that IR waves will reflect off surrounding structures and create signal interference. This provides 100 percent read rates inside the zone and zero reads outside of it. The interrogator can even read an IR tag if the line of sight between the tag and reader is partially but not totally obstructed. This limitation does not pose any problems for the Höganäs deployment because the interrogators are positioned to have a clear line of sight with the tags.

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