By Samuel Greengard

July 30, 2007—Putting an RFID system in place presents numerous challenges, yet few loom as largely as determining how and where to use interrogators (readers) in distribution centers, warehouses or other facilities. Today, thanks to the widespread adoption of wireless local area networks (WLAN) and the introduction of Bluetooth technology, the decision-making process is increasingly complex. Organizations can choose between traditional fixed interrogators, handheld interrogators and newer mobile readers designed to mount on a forklift or other vehicle, or even reside on an employee's body.

Fixed readers are built for large-scale deployments at fixed locations and have the capability to read high volumes of tags. They detect any tagged object that passes near them—typically within a range of 10 to 20 feet for passive tags and up to 300 feet for active tags. Fixed readers require connection via cables to external antennas, a power source and a middleware system that will manage the RFID read data.



Handheld interrogators, which are battery-powered, provide greater latitude over where, when and how they can be used. But a user needs to trigger a handheld device, and the read zone is determined by where it is aimed. Handheld interrogators can take different forms and include an array of features and functionality. Some are handheld computers with an interrogator that is inserted into a PCMCIA card; they are effective for reading tags on a few objects. Others are gun-like devices that feature fully integrated RFID antennas and far more powerful read capabilities. Still other more powerful handheld readers include bar-code scanning and provide a touchscreen display. In the early stages of an RFID implementation, handheld interrogators often serve as a bridge between the worlds of bar code and RFID.