Best practice for your RFID system.
RFID is a reliable technology but like all electronic systems it has its limitations. If tags can’t be read as expected it is easy to blame the technology (tags or readers) or the application. Often though it’s not their fault.
We find the most common cause of poor rfid performance is poor tag fixing. How you manage the deployment of your tags can greatly affect the success of your system. That is why we have put together this guide to the best practice in fixing tags. Here’s how to avoid the most common pitfalls …
1. Take Care With On-Metal & Non-Metal Tags
Tags are often designed to work in conjunction with the item they are attached to. This can influence the way that they are read, their speed to respond and the distance over which they can be read. Attaching an on-metal tag to a non-metal surface and vice-versa will mean reduced performance.
Some tags are suitable for either type of surface but most are only suited to being mounted on metal or non-metal surfaces. You may need different types of tags for different types of item in your system.
Make sure you select the correct kind for your application and then check when tags are attached that things are as you expected. If you have to fit to many different types of item, then consider this when you are selecting your tags and carry out a trial of the various materials involved.
2. Don’t Bend, Fold or Twist Tags
Most tags are quite robust but remember that embedded in that sliver of plastic or paper is an electronic chip linked to an antenna. On some tags, especially label types, bending, folding or twisting tags can result in the links between the antenna and the chip being broken. If this happens the tag cannot react.
Some tags can even be sensitive to the touching the chip or antenna.
3. Follow The Fixing Rules
First of all you have to make sure that you have the right type of tag for the item that you are tagging.
A tag needs to be fixed firmly to the item that it is intended to identify. If tags become separated from items then they cannot do the job that they are supposed to. Following the fixing rules for a particular type of tag will mean that the tag will work more reliably AND there will be less chance of it becoming separated.
Some tags are meant to be fixed to assets using adhesive, some with screws or rivets. Some are meant to be embedded beneath epoxy and some are meant to be attached with loose fixings such as cable ties. When tags are designed the expected method of fixing is taken into account and using the wrong type of fixing can significantly affect the distance from which a tag can be read.
Using the wrong type of fixing can mean that tags aren’t read properly or worse still that tags become detached from the item they are intended to identify. If using adhesives make sure that:-
·The surface for attachment is perfectly clean and flat.
·The correct adhesive for the type of tag and items it is attached to is used.
·The adhesive is used according to its specification (especially ambient temperature).
·Adequate time is allowed for the fixing to ‘cure’.
If you are using screws, bolts, cables or zip ties to fix tags choose your fixing depending on whether or not the tag will be outdoors so as to avoid the risk of tags becoming detached as a result of rusting fixings. When fixing with screws or bolts, be careful to tighten the fixing sufficiently to ensure it will not come loose but not so tightly as to distort the tag. Some zip ties may be liable to degrading in UV light and so not suited for use in outdoor applications.
If you are using tag fixing methods that aren’t easily undone (adhesive mounting, embedding, or rivet mounting for example) then check the tag is working and assign the tag-id to the relevant asset on your computer system BEFORE fixing the tag to the item.
For stitched tags used with garments, ensure that stitching is only in the allowed area. Failure to do this might cause the circuits between the antenna and the chip to be broken.
For animal tags or tags attached with plastic fixings studies have shown that attaching tags at low temperatures (well below zero Centigrade) may affect the reliability / durability of the tag fixing even if the tag is rated for use at that temperature.
If you are planning a big deployment of tags, perhaps involving temporary staff to fix tags, and maybe involving different tags types for different equipment types, the team will need a thorough briefing as to what is expected. It is almost certainly a good idea to have the team tag a few items and then do an inspection to ensure that there hasn’t been any confusion about how tags ought to be applied.
4. No Staples, Pins, or Paperclips.
This is for the same reason as not folding, bending or twisting tags. It’s quite possible for a staple, pin or paper clip to break the circuitry of a tag, making it useless.
Surely no one would be silly enough to staple a tag to an item? Well, don’t forget that some tags simply look like printed labels and if staff don’t realise there are thin wires inside it can be easily done.
5. Use The Right Location / Orientation
Tags need to be located so that they have the best chance of being read accurately. Some tags will have a different field of detection horizontally to vertically so that how they are mounted, square to an edge or at an angle, can really affect from how far away they can be read. This is particularly true if tags are being used in conjunction with fixed location readers and antennas. Positioning a tag incorrectly can reduce the effective reading distance by more than half.
The “right” location needs to be thought about from the point of view of mounting the tags (it is no use expecting them to be put where staff cannot easily get) and reading the tag (if a tag is fitted during an assembly process, for example.)
If the tag is designed to operate over a short range (typically low frequency and high frequency tags) will it still be accessible when the item is in the field and the tag needs to be read? Make sure that such tags are located where they can be reached.
It is also a good idea to think about how the item the tag is attached to might affect the tag. For example-
·If you are tagging crates or pallets can the tag be placed where it won’t be affected by stacking or when the item is being transported.
·If you are tagging items that are lifted with slings or fork lifts make sure that the tag is fitted where the lifting gear won’t foul it.
·If your tag has information that you expect people to be able to read, or if they are colour coded for some reason, make sure they are located where they can be seen.
It’s a good idea to document the tag fixing rules for your particular application and make sure that anyone fixing tags is trained in them. An example for tagging motor vehicles might read (although a illustration might be better)…
“The tag must be mounted on the inside of the left side of the wind screen, 1cm from the window pillar and 10cm from the top of the windscreen with the tag’s long axis parallel to the window pillar and the manufacturer’s logo at the top.”
It may even be worth creating a “fixing jig” to make it easy to get the right location if tagging a large number of similar items.
6. Follow The Temperature & Humidity Rules.
Tags need to be kept within their environmental limits – especially temperature and humidity. The electrical circuits may not like it hot and dry or cold and damp. There are tags of differing specifications so it’s important to choose an appropriate tag in the first place and especially tags need to meet the worst extreme that will occur during their lifecycle (often a particular problem for tags used on items during manufacture or subject to harsh cleaning).
If applications change and the temperature or humidity range that the tagged item goes through changes, then you may need to rethink your choice of tag. This rule also applies to the time when tags are stored but note that the specifications may be different for tags in storage and tags in use.
Suppliers should be able to provide you with the relevant specifications for your tags.
7. Watch Out For Metals, Fluids & Motors
Strong electro-magnetic fields, especially near powerful electric motors, dynamos, relays and the like, can disrupt tags but are more likely to just interfere with the tag reading process. It is probably not a good idea to store tags in a room next to lift motor, for example.
Equally tags can be prevented from being read by a metal item standing between them and the reader (for example a stapler left standing on the lid of a closed lap top might well interfere with successful reading of the tag on the rear of the lap top).
Liquids can interfere with successful tag reading too; don’t put a tagged filing folder on top of the office aquarium!
8. Make Sure Everyone Knows What Tags Are For.
If staff do not know the importance of tags to your business, then you are losing essential allies in your fight to make your system a success. If someone removes a sticky tag from a crate just thinking it’s a blank label then keeping track of the crate is made impossible. It might be a quite unintentional action but its impact could be significant.
If staff are not properly briefed about how to apply tags, they may be placed on assets in a way that makes them less likely to be read successfully.
Some staff may also be concerned about the deployment of RFID tags. Disinformation about what RFID tags can and cannot do can be found on the internet and popular misconceptions about RFID and privacy, for example, may affect staff attitudes to the system and so, its potential success. Clear communication with staff about the purpose of the system and the way that the technology works is the best way to avoid problems.
9. Keep Control of Your Tags
Do you know where your tags are? Do you know where they have been? Do you know who can get hold of them?
There are several reasons why it is a good idea to have a system to keep control over the tags used in your systems. For example:-
· Ensuring that tags are kept in known locations makes it easier to ensure that they are stored within the recommended environmental conditions.
· Keeping tags under control makes it easier to ensure that only authorised staff attach tags. This will help to make sure that tags.
· Controlling tags makes it easier to control the process of associating a tag with a particular item, so reducing the risk of for example,double tagging an item or linking the wrong tag id to a particular asset.
· If you aren’t sure of your stock of tags you may run out at a time when you need to tag a new batch of items, causing delays as a result of order lead times.
· As far as a computer system is concerned the tag equals the thing it is meant to have been attached to. If tags are not kept under control there is a risk that they may be used fraudulently to mislead systems.
· Tags can be valuable – loss of tags means lost cash and may mean that tagging of items has to be delayed if tags that you thought were available cannot be found.
· Tag specifications change over time. RFID like all technology, is subject to constant innovation. What happens if you need extra tags at some point in the future and then only different ones are available? Although electrical and communication standards have been quite stable there have been changes in some tags’ microchips which could alter the performance of one tag compared with another. And what if a manufacturer has a quality problem? Will you be able to identify which batch of tags was used on which items at which location?
· If your application uses tags as consumable items then make sure that you have an adequate stock to allow for the lead time in ordering additional tags. Most tags are manufactured in the Far East and some suppliers only hold limited stocks in Europe.
It isn’t necessary to have a complicated system but it is a good idea to make sure you know what you have, where they are and who has access to them.
10. Don’t Re-use Tags
There are two reasons for not attempting to re-use tags.
Firstly there is a risk of damage to the tag. This particularly applies to tags that have been attached to items with adhesive. Some tags are specifically designed to break the connection between the tag’s antenna and the chip if they are removed from the thing they are attached to (so-called anti-tamper tags). Even so, if any tag is pulled from the item it has been attached to there is a risk of damaging it internally.
Secondly, quite apart from these physical problems, it is good practice not to re-use tags UNLESS your system has been designed with this in mind.
There is a real risk of confusion arising in back-end systems where the one tag identity becomes linked to two or more items on a computer database or two different tag identities get linked to the same physicalitem. If this happens it creates the potential problem that assets will become “lost” in the system or, if a system is collecting the life history of an asset for example, that only part of that life history will be accessible.
Using tags only once avoids these problems.
