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Howto : choose a RFID tag for industrial applications

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Choose a RFID tag for industrial applications is not a simple thing : technology, price, performance, resistance (temperature, dust, etc.), compatibility with the object to follow, are different parameters to consider. Nexess presents in this post a”Howto” to choose the right RFID tag for industrial applications.

Passive, Active and Semi-Passive : which RFID technology for my application ?

To choose the right RFID tag you will use for your application, let’s first have a look of the technologies available on the market :

  • The passive RFID tag : as its name suggests, this RFID tag is purely passive, meaning it does not include a battery. The passive tag uses the wave (magnetic or electromagnetic) from the interrogator (RFID reader + antenna) to supply the electronic circuit built in. It may contain information in its memory. This is the most common tag on the market.
  • The semi-passive RFID tag (BAP Battery Assisted Passive) : the tag embeds a power supply (battery). The power is not used to provide energy to a transmitter because the principle of communication is equivalent to passive RFID tag. This energy is typically used to supply power to the electronic circuit of the tag or sensors connected to the circuit for example (temperature, intensity, acceleration, gyroscope, etc.). This type of tag theoretically offers higher performance compared to passive RFID tag (reading distance). This type of tag is generally used for special applications : temperature measurement, flow of people, etc. These tags require maintenance due to a frequent change of batteries. They represent less than 15% of sales of RFID tags in 2012.
  • The active RFID tag : This tag embeds a radio frequency transmitter and therefore a power supply (battery). As semi-active tag, it can be equipped with sensors (temperature, gyroscope, GPS, etc.) and embeds intelligence in the form of a micro-controller for example. This tag can autonomously interact in real time with its environment through its battery : sending its position, taking temperature, etc. These tags require the establishment of a communication structure (nodes, antennas, readers) to “surround” an area, a building, etc. They also require maintenance related to the replacement of batteries, more frequent than semi-active tag. They represent less than 15% of sales of RFID tags in 2012.

These three descriptions already point to the right RFID technology to use in terms of benefits and technical requirements. But a deeper analysis regarding the needs of traceability is necessary to ensure that the technology will answer correctly the needs :

  • The object to follow should be geolocated at any time ? In the building or outside ?
  • The object to follow must be detectable via a reader with contact (<1m), medium distance (<10m) or long distance (> 10m) ?
  • How many objects to follow ?
  • What is the size of the object to be identified ?
  • What is the value of the object to be identified ?
  • The tag have to follow the complete life of the object ?

Choose a RFID tag for industrial applications : the passive tag, 4 frequencies, 4 features

Choose a RFID tag for industrial applications should be guided by its use and future expected performance.

Below some typical questions :

  • How far away the object should it be identified / examined : a few centimeters, several meters, tens of meters ?
  • Is my industrial plant subjected to EMC constraints ?
  • Is the object to follow metallic ?
  • The object to follow contains liquid ?
  • Should we quickly identify a large number of objects ?

The answer to these questions will guide the choice of the passive tag and its associated frequency. Indeed, there are four frequencies with different characteristics :

  • LF (Low Frequency) : between 125 and 134.2 KHz. The maximum detection range of a tag corresponding to this frequency is about 50 centimeters. Characteristics associated with this frequency range are : high prices even with large volumes and low impact on reading performance in metallic or liquid environment.
  • HF (High Frequency) : frequency of 13.56 MHz. The maximum detection range of a tag corresponding to this frequency is about one meter. Characteristics associated with this frequency are : lower prices than LF tags, adapted to applications requiring reading with contact and without large volume of tags to read and overall frequency (the same in all countries).
  • UHF (Ultra High Frequency) : frequency between 868 and 915 MHz. The maximum detection range of a tag corresponding to this frequency is about 3 to 10 meters. Characteristics associated with this frequency range are : lower prices than LF and HF tags for large volumes, adapted to applications requiring reading distance and a large volume of tags to be read very quickly and tags dedicated to constrained environments (metal, liquid, etc.).
  • SHF (Super High Frequency) : between 2.45 and 5.8 GHz. The maximum detection range of a tag corresponding to this frequency is about 1 meter. Characteristics associated with this frequency range are : performance quite similar to the UHF, high sensitivity to metal and liquid environments and directionality of detection tags.

choose an RFID tag for industrial applications

According to the study ” RFID Forecasts, Playersand Opporunities 2014-2024″ of IDTechEx, the valuation of the number of passive RFID tags which will be sold on the market in 2020, all applications and markets taken together, are presented hereinbelow :

  • LF : 1308 million (646.5 in 2013)
  • HF : 5904 million (2182 in 2013)
  • UHF : 30000 million (3079 in 2013)

Ratio Cost / Performance : good compromise

Choose a RFID tag for industrial applications requires an analysis of the cost / performance ratio to optimize the return on investment (ROI) of the  implementation of the RFID solution.

RFID passive tag case

There are many suppliers of passive RFID tags on the market, offering specialized lines in specific sectors and applications : logistics, retail, harsh environments, aeronautic, etc. The choice of passive RFID tags is overabundant and can sometimes be complex when it comes to differentiate them at the technical level / cost or in real performance test on the field.

Several criterias have a significant influence on the price of tags but also their performance. Some elements are listed below :

  • Harsh environment (explosive atmosphere) : tags certified ATEX are noticeably more expensive because they have a special design to answer to the requirements of ATEX standard. Certification cost has also an impact on the price.
  • Size of the tag : more a tag is small with a high search performance (distance of reading of 1 meter with portable player), more its price will tend to be slightly higher than the others. This statement can be observed especially for small ceramic tags compatible with the metal that require special design.
  • Volume : As any consumable, the price of a passive RFID tag reduces a lot with the volume of the planned purchase. The first significant levels observed are achieved for several thousand of units.
  • Application : If the seeked application is very special indeed almost unique and requires a particular design or packaging, the price tag can really increase. Take the example of a tag requiring resistance to high temperatures ranges, chemical attack, etc.
  • Memory : If the tag must store information whith a volume greater than the standard memory of 512 bits, it is necessary to appeal high memory tags (2 Kbits to 64 Kbits). We can observe a noticeably higher price than conventional tags but also performance reduced especially the write distance (count 40% of the reading distance).