When Should You Use Active Tags

Active tags can broaden your benefits, accelerate ROI

Active tags are battery powered and provide a much greater read range than passive tags. Of course, an active tag's read range varies based on its transmitter strength, power, antenna size, frequency, and on climate conditions. Some tiny tags can read up to 15 feet away, and there are brick-sized tags that read up to 3,000 feet away. Many different active tag frequencies are used, the most common being the 433 MHz range. This frequency is less affected by moisture and metal than the 915 MHz or 2.45 GHz range and are typically found in outdoor applications.

RFID Tags with Built-in Sensors

Active tags can provide other significant benefits over passive tags besides greater distance. A battery allows other sensors to be built directly into tags. We'll describe a few examples of how this technology is currently used, and will add many more examples and case studies, so check back to this section often.

Environmental Sensors:

Sensors can let tags report whether a location is too hot or too cold, if certain gasses or liquids are present, and even if hazardous or radioactive elements have been detected. A tag can measure air temperature, humidity, elapsed time, etc., and then store the information in memory.

One poultry company discovered that their shipper was turning off their trailer's freezer when transporting frozen chicken, turning it back on prior to arrival. Detecting the potential meat spoilage hazard was of incalculable value to the chicken farmers. And Boeing reported that using sub-zero RFID sensors reduced spoilage of valuable gasses that must be stored as liquid in sub-zero temperatures.

Thieves beware:

Tags with vibration or motion sensors are used for security purposes at Paris' Musee du Louvre. The museum mounts motion-sensor RFID tags on the backs of paintings. If a painting moves, the tag signals a reader mounted up to 100 meters away and guards are instantly notified which painting moved. Larger versions of this same hybrid RFID technology are used to guard containers for international shipment and in homeland security applications.

Real Time Location Systems (RTLS)
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RFID helps locate items in at least two ways. GPS sensors can be combined with tags, broadcasting assets' locations. One manufacturer reported using a version of this in manufacturing to modify laser cutting of various items on an assembly line.

Real Time Location Systems (RTLS) use active tags and a technique called 'triangulation' to determine an asset's location. Based on the time it takes an active RFID tag's signal to reach a reader, the distance from that antenna can be measured. By combining data from three or more readers, an X-Y position can be determined; additional devices can determine the Z coordinate. This type of solution is ideal when expensive assets are frequently moved in a large facility.