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Best practice when fixing RFID tags

How to avoid the most common pitfalls

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 but often that’s not the cause of the problem.

We find the most common cause of poor RFID performance is poor tag fixing. How you deploy and manage tags can greatly affect the success of your system. Our ten-point guide to best practice in fixing tags will help you avoid the most common pitfalls.

1. Take care with on-metal and 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 of response and the distance over which they can be read. Attaching an on-metal tag to a non-metal surface and vice-versa will reduce performance. Although some tags are suitable for either type of surface, most are only suited to one or the other.

You may need different tags for different items in your system, so make sure you select the correct type and once attached, check the performance is as expected. If you have many different types of items, take this into account when selecting tags and carry out trials.

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 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

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 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.

The tag needs to be fixed firmly to the item – if it becomes separated it cannot do its job. If you follow the rules for fixing that particular type of tag, it will work more reliably and there will be less chance of it becoming separated.

Some tags are meant to be fixed with adhesive, some with screws or rivets, others embedded beneath epoxy or attached with loose fixings such as cable ties. The design of the tag takes account of the method of fixing so the wrong fixing can affect the distance from which it can be read. It can also mean that tags aren’t read properly or become detached.

If using adhesives, make sure that the surface is clean and flat, you are using the correct adhesive and in according with the specifications, especially the ambient temperature. Be sure to allow adequate time for it to ‘cure’.

When using screws, bolts, cables or zip ties, choose the fixing depending on whether the item will be indoors or outdoors. Be careful to tighten screws or bolts sufficiently so they will not come loose, but not so tight as to distort the tag. Some zip ties are liable to degrading in UV light and are not suited for use outdoors.

If you are using adhesives, rivets or other methods that aren’t easily undone, check the tag is working first and assign the tag-id to the relevant asset on your computer. For stitched tags used with garments, ensure that stitching is only in the allowed area to avoid damaging the circuits between the antenna and the chip.

With animal tags or tags attached with plastic fixings, studies have shown that attaching them at low temperatures – well below zero Centigrade – may affect the reliability and durability of the fixing even if the tag is rated for use at that temperature.

If you are planning a major deployment with the help of a team, give them a thorough briefing first. Then have them tag a few items and do an inspection to ensure that there is no confusion about how tags ought to be applied.

4. No staples, pins or paperclips

Just as it is inadvisable to fold, bend or twist tags, it is also wise to avoid the use of staples, pins, paper clips or other items that could break the circuitry.

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. Ensure they are located in the right place

Tags need to be located where they have the best chance of being read accurately. Some tags will have a different field of detection horizontally to vertically so how they are mounted – whether square to an edge or at an angle – can affect the range. This is particularly true if tags are being used with fixed readers and antennas. Positioning a tag incorrectly can reduce the effective reading distance by more than half.

When choosing the ‘right’ location you need to consider how accessible it is from the point of view of mounting and reading. If the tag is designed to operate over a short range, can it still be read when it is in the field? Can staff access the item to mount the tag?

It is also a good idea to think about where on the item the tag is attached. For example with crates or pallets, can the tag be placed where it won’t be affected by stacking? If items are to be lifted with slings or fork lifts make sure that the tag is fitted where the lifting gear affect it. If the tag is colour coded or has information on a label, make sure it is located where it can be easily 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. Give clear instructions including any measurements and, if you are tagging a lot of similar items, consider creating a ‘fixing jig’ to make it easy to get the right location.

6. Follow the temperature and 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. Tags come in a huge range of specifications so it’s important to choose ones that are appropriate and consider the worst extremes they will face during their lifecycle. This is often a problem for tags used on items during manufacture or subject to harsh cleaning.

If applications or environmental conditions change, you may need to rethink the choice of tag. 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 and 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 a lift motor, for example.

Equally the signals can be blocke by a metal item standing between the tags and the reader – for example a stapler left on top of a closed laptop might interfere with successful reading of the tag on the rear of the laptop. 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, then you are losing essential allies in your fight to make your system a success.

If someone removes a sticky tag from a crate thinking it’s a blank label, then keeping track of the crate is impossible.

If staff are not properly briefed about how to apply tags, they may place them 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 due to misconceptions about privacy or misinformation. Clear communication about the purpose of the system and the way it works is the best way to avoid problems.

9. Keep control of your tags

It is a good practice to have a system to manage the tags so you know where they are and what type, and control how they are deployed. This will help avoid mistakes such as double tagging, ensure they are stored in the right conditions and reduce losses. As tags can be valuable, costs can soon mount.

If tags not kept under control, in some cases there is a risk that they may be used fraudulently to mislead systems.

As specifications change over time, you need to record which batch of tags was used on which items in the event you need to replace them. Business which use tags as consumable items should also make sure they have an adequate stock to allow for lead times – most in the Far East and suppliers may only hold limited supplies.

10. Don’t re-use tags

There are two reasons for not attempting to re-use tags. Firstly there is a risk of damage, particularly when tags have been attached with adhesive. Some – anti-tamper tags – are specifically designed to break the connection between the antenna and the chip if they are removed but this could occur where any tag is pulled off an item.

Secondly, 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 in back-end systems where one tag identity becomes linked to two or more items on the database or two tags become linked to one item. If this happens assets can become ‘lost’ in the system or the system will only be able to access that part of an asset’s life history.

Help with troubleshooting

CoreRFID is a specialist in RFID-based applications and offers a consultancy service to help with selection and deployment of RFID tags and carrying out trials. We also offer a troubleshooting service.