Telling the difference between passive and active RFID tags

Everything you need to know about RFID tags

RFID tags are a critical component of RFID asset tracking solutions. They can be affixed to a range of objects including assets, inventory, vehicles and even people as part of a customised RFID technology solution.

RFID, or Radio Frequency Identification, is a form of wireless communication that uses radio waves to identify a wide variety of tagged objects or people from a distance. RFID tags work as part of an integrated technology solution that includes RFID readers (static or handheld), RFID printers and software to capture and manage data that pinpoints object location, tracks movement and is capable of recording a wide range of other information. 

RFID tags vs barcodes

The development of RFID technology over a number of years has resulted in RFID tags (as part of a larger, integrated solution) becoming a valid replacement for the traditional barcode. There are two key differences between RFID and barcodes:

  1. Unlike barcodes, RFID does not need a direct line of sight to see an object. This is important when there are thousands of objects in a room, and saves time going from item to item to record them one by one. RFID readers can be ‘swept’ across a room and separately record all the items inside.
  2. Barcodes are static and cannot store detailed information. RFID tags are ‘smart’ and can store and transmit a lot of data via readers back to software and databases for real-time information on movement, status and location. This is extremely useful to track inventory as it moves through a supply chain from production to purchase. 

Another key difference is that, unlike barcodes (which are of a standard format), there are various different kinds of RFID tags – one size does not fit all. The choice of the most appropriate type of tag will be part of an overall RFID technology implementation strategy, and will be chosen based on tagging and tracking scenarios and applications, including of course, what needs to be tracked. 

Choosing an RFID tag that is fit for purpose

While the term ‘RFID tags’ is widely used as a catch-all descriptor in the industry, the first thing to understand is that tags can take many forms including stickers, adhesive labels, hang tags and hard tags that suit any environment. 

Deciding on what tag will suit a particular application comes down to a range of factors that include:

  • The object being tagged, and where the tag needs to be placed for optimal reading
  • The surface upon which the tag will be affixed (metal, plastic etc.) and if it is unusual or irregular
  • The physical stress the tag may be subjected to, such as commercial linen or extreme weather conditions for objects in the field
  • If the tag needs to be wearable by a person, such as on a wristband or fob

Finally, and very importantly, is whether RFID tags in a particular application need to be active or passive.

Active or passive RFID tags – what’s the difference?

Aside from any other consideration as outlined above, the biggest factor to consider in choice of tag for an RFID solution comes down to whether the tag is active or passive.

Active RFID tags have a transmitter and their own power source, such as a battery. Power is provided to run the circuitry of the tag, and also to transmit or broadcast a signal to an RFID reader. This is similar to how a mobile phone sends a signal to a cell tower. Active tags are ‘always on’ and broadcasting their signal whether in range of a reader or not

Passive tags do not have a battery or power source. Instead, they draw power from the RFID reader that sends out electromagnetic waves that create a current in the antenna of the tag. These tags lie dormant until they get a signal from a reader.

There is one other kind of tag to be aware of – semi-passive (or semi-active if you prefer). This type of tag uses a battery to run the tag circuitry and hold data, but it does not actively transmit. Instead, it relies on a reader to power its ability to communicate when in range. 

How to choose the right tag for an RFID solution

Choice of tag will depend on the application of the tag in the context of an integrated RFID asset tracking technology solution, the objects to be tagged and how objects are read. Cost is also a factor to be considered.

Cost: Active tags are technically more sophisticated to carry more data and send a signal, and require an internal power source, making them relatively more expensive compared to passive tags. 

Size: Passive tags can be very small, but active tags are larger and bulkier due to the embedded battery.

Disposability: Tags affixed to assets such as vehicles can remain there for many years. However, tags affixed to fast-moving products such as clothes and consumer goods cannot be retrieved and reused post-purchase. 

Read range: Active tags have a much longer read range (say 50m to 300m) than passive tags (50cm to 15m).

Signal: Passive tags only transmit when triggered by the proximity of an RFID reader, whereas active tags are always on.

Life span: Depending on the treatment they are exposed to, passive tags have an infinite life span, generally at least 10+ years. On the other hand, due to battery life, active tags have a life span of around three to five years. 

Embedded: Passive tags can be easily embedded within objects, but due to their size, this is difficult for active tags. 

In general, and due to the combination of factors outlined above, passive tags tend to be used on smaller items. For example, inventory items moving through a retail supply chain in high volumes, with disposability post-purchase, suit the use of passive tags which can be small enough to use on clothing and other consumer products.

Passive RFID tags can also be used for smaller classes of assets such as computers, tablets and mobile phones. 

On the other hand, larger and more expensive active RFID tags are more suitable for bigger assets such as cars, trucks and other equipment that moves over wider areas such as depots, warehouses, building sites, vehicle dealerships and ports. 

Semi-passive RFID tags are typically used in situations where an object needs to internally record information such as temperature, pressure, relative humidity, acceleration, vibration, motion and altitude. The tag then communicates this data when transmission is triggered by a proximate reader. 

Before you choose an RFID tag, choose Australia’s leading RFID specialists

RFID tags are an important part of an integrated RFID asset tracking technology solution. The right choice of tags, combined with RFID readers and software, helps create a powerful RFID solution to increase the visibility of valuable assets, save time, reduce costs and increase the bottom line. 

RAMP are the leading RFID specialists in Australia and can provide advice and assistance for the  design and implementation of a customised  RFID technology solution for the specific needs of your business.