Active RFID versus Passive RFID

As RFID technology moves forward, choosing between active and passive technologies becomes more and more of a challenge. Although both technologies offer excellent features, you still need to understand how the technology works before starting an implementation. Whether you’re tracking product through a production line, or you are keeping track of equipment, the right solution for you depends the application and your budget.

Brief

Active RFID

Active RFID uses battery power within the tag to continuously broadcast a signal. Because of the battery, individual tags tend to have a higher cost than their passive RFID tag cousins. This technology allows for much great distances and accuracy than passive RFID. Active RFID comes in many flavors, and depending on the beacon technology being used, the readers themselves can be very inexpensive. Active RFID networks can be implemented with wired readers, Bluetooth technology with smart phone apps, or can be part of a smart mesh networks where the tags hold unique ID’s, but also work together to communicate their information back to a main reader.

 

Passive RFID

Passive RFID uses tags that require no internal power. The RFID antennas send out an electromagnetic signal and the passive tags reflect a signal back with its unique information. These tags tend to be much less expensive than Active tags because the require no internal battery. The distance the tags can be from an antenna is usually less than 15 feet (generally shorter than an active RFID solution).

 

Detail

Passive RFID Details

When implementing passive RFID you will need the following three components:

 

• RFID Reader
• RFID Antenna(s)
• RFID Tags

 

The readers are usually connected to the network using standard Ethernet cables. Many readers are now capable of using power over the Ethernet (POE), meaning you don’t need extra cabling for power. Some readers have the antenna embedded into them, but most have external antennas. The antennas are usually connected to the readers using standard coaxial cable. These readers come in assorted flavors, UHF, HF, and LF. The LF and HF technologies are for applications at a very close range, such as access systems or close-range manufacturing applications. UHF is for larger distances, such as tracking product and assets through portals.

 

Antennas come in all shapes and sizes depending on the application. The most common antenna is about a one foot square device. The antenna can be placed at different angles and heights to give you the best read-zone success rate. Multiple antennas can be placed in a zone to increase the read rate and decrease the chances of missing a read. You can reduce or increase the power the antenna sends out to adjust the distances at which the reads will occur.

 

Passive RFID tags come in many shapes and sizes. Each tag contains a circuit with an internal antenna. This circuit receives the electromagnetic signal and reflects its own unique information back out for the antenna to capture and read. The larger the tag, the better the chance the tag will receive the electromagnetic signal from the antenna.

 

Other factors to consider is the environment where the tags and readers will be located. If there is lots of metal or liquid in the area, the chances of reading a passive tag decreases. Also, if the tag is going to be placed on metal, then a special tag is required that will not ground the circuit enabling the tag to still reflect its signal back to the antenna. These tags, as well as pretty much any form factor, can be purchased through specialized RFID tag suppliers. Express Corp (www.expresscorp.com) is one such company, who can supply many different form factors and also meet customized needs such as barcodes, imagery, and human readable text.

 

Active RFID

Active RFID uses batteries to power tags and sometimes the network itself. Each tag transmits its signal to a receptor or a beacon reader. Higher sophisticated systems may even have their own mesh network allowing tags to relay their information through other tags.  Other benefits of a mesh network can allow for the use of fixed location tags that allow the mobile tags to calculate and transmit their own location in the grid.

 

Because active tags require a battery and are typically smarter than passive tags, they are usually 5 to 50 times more expensive than passive tags. However, the readers and antennas for active technology are usually much less expensive than their passive cousins.

 

Active technology is usually much easier to install because the readers and antennas tend to be much smaller with read ranges much greater. In some cases, an active tag can be read at over 300 meters. Reference points can also be triangulated easier with active tags, giving pin point accuracy of the tag’s location.

 

More maintenance may be needed for active technology because batteries or tags may need to be replaced every three years or so, depending on the transponder frequency (how often the tag sends out its signal).  Some active tags enable the readers to determine the remaining battery life within the tag enabling a more efficient maintenance plan.

 

Summary

Both active and passive RFID are now adopted, widely used and quality technologies. Which one is right for your application depends on the frequency you read, how your site is situated, and how much distance you need to read your assets. And, of course, your budget.

 

The experienced staff at InformaTrac will be more than glad to provide you with a free consultation.  Feel free to call at (866) 619-7411 or click here for more information.

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