RFID on the Production Line
an popping up, users started running applications with smaller memory tags, which were linked to central databases and enterprise systems.'

Though they've shrunk to cookie-sized and smaller and their cost dropped to a few dollars or less over the years, these tags are still reused hundreds of times in closed-loop applications, diluting initial implementation costs. They're typically used to track big-ticket items, such as automobile chasses and components, which also helps make them economical

ly worthwhile.

'Traditional RFID tags work almost like an extended hard drive, and users can read and write onto them all the data on the quality measures that need to be achieved,' says Alec Stuebler, Siemens Energy & Automation's business manager for factory automation sensors. 'For example, an RFID tag can help confirm that tools measuring torque during automotive assembly meet pre-defined measurements, and then allow components being assembled to move to the next step. Or a heat-resistant tag can help start a paint process, and then verify quality when it comes out of the 250 °C oven.'

Steubler adds that read ranges for RFID tags can vary from 2 mm for flush-mounted tags in tooling applications to 2.4 GHz tags that can read at 300 meters. Memory sizes can range from 96-112 bytes up to 64 Kbytes, though more memory may require added power, such as a battery, to keep that memory active and accessible.

RFID systems usually operate at three main frequencies: low frequency, which is below 1 MHz; high frequency, which is the 13.56-MHz universal frequency required worldwide for scientific instrumentation; and ultra-high frequency (UHF), which is over 800 Mhz. UHF allows longer range and is less costly, though it reportedly has some interference issues.

Siemens plans to introduce its Simatic RF 600 and Simatic RF 300 products in August 2005. Reportedly able to achieve a 3-5 m read range, these 900-MHz systems will include RFID tags, readers, antennas, and software.