Wednesday 26th Oct 2016 - Logistics Manager

Not the Laws of Physics again: Chris Wright

I attended an RFID seminar just recently where the presenter was bemoaning the fact he kept hearing the phrase: RFID is difficult you know – you have to understand the “laws of physics” suggesting of course that it was, a) part of the hype associated with RFID or that, b) he had cracked the problems and it had nothing to do with physics and by inference it wasn’t difficult.

Well, I am going to discuss the laws of physics – with no apologies because it is essential to know that tags are affected by the presence of metal, water and electrical noise as well as other factors. I’m going to target the effect of metal on RFID tags, particularly UHF Gen 2 tags. I’m going to offer a solution.

First, the business requirement and the problem. Utopia is every item being tagged and successfully tracked without human intervention through the supply chain. The business benefits of this are enormous; accurate stock control; the ability to match supply to demand and to remove the cost of stock control.

The problem is that in practice it’s not as easy as it sounds. Focusing on moving metal items through the supply chain, items such as toys, PCs, garden equipment, and especially the wire cages that these items get moved in, then the challenge is that you cannot use the same tags as though the item was a plastic tray, or fruit and veg, or clothing. The trouble is that standard RFID tags when they are applied to metal don’t work. The law of physics that relates to this is the faraday cage effect. (Lots of people stretching back to school days at this point.)

However the business case for tracking wire cages and getting them back is worth it on its own. I have heard tales of retailers having to replace 25 per cent of their stocks every year as they go missing. A lot of money when they cost around £90 a cage.

Fortunately there is an answer – on metal UHF Gen2 tags which although directional do allow you to place the tags on the metal itself and not lose signal. Using these tags to track wire cages will provide immediate return on investment as all the benefits of accuracy, visibility, cost reduction and control when using RFID can be applied.