A number of years ago, the team from Seritag created the ScanStrength NFC tag performance rating system to help customers select tags. The ScanStrength scale ran from 1 to 10 where 10 was the NFC tag with the furthest tag scan distance and 1 was the tag with the shortest. In 2019, Seritag launched the Real ScanStrength which tests each tag with 12 of the most popular mobile phones and provides a actual average scan distance in mm.
Then, in 2023, Seritag built an entire intelligent scanning machine to simulate not only the average tag scan distance but also the performance from a mis-aligned phone. This is ScanStrength+.
ScanStrength is how close you need to hold your mobile phone to the tag before it responds.
Seritag use a custom built machine which has been calibrated using machine learning (AI in today's parlance) to create a model of how a selection of the current most popular phones would scan an NFC tag. Each tag is placed into the machine which automatically simulates scanning from different angles and with different antennas and power loads.
The end result is a scan distance - in mm - which reflects the real world scan performance of the average mobile phone.
Unlike Android phones which are generally consistent in scanning performance from 'background' no-app scanning and in-app scanning, the iPhone substantially increases the power when scanning from within an app.
Our machine learning model takes this into account when considering the ScanStrength+ distance rating. However, clearly, customers will notice that in most cases, the scan performance will be lower on an iPhone outside an app and then better from within an app.
Of course, as a number of NFC tags are designed to work on metal - typically called 'on-metal NFC tags' - the ScanStrength+ system also measures the performance of tags when used on metal.
In addition to the standard ScanStrength ratings, we also test the performance on the tags when the phone isn't perfectly aligned with the tag. To give some indication of this performance we also provide an 'offset' rating which runs from 50-100% and <50% - where 100% indicates an extremely good performance when the phone isn't perfectly aligned with the centre of the tag.
It's clearly important to note that ScanStrength is an average and that there's often quite a bit of variance between phones.
The purpose is to give you some indication what you might expect and importantly how one tag might compare to another. As with all things technical, we strongly advise you to understake testing to get the best indication of the scan distances you can expect for your project.