The science behind our tags

Radio frequency identification (RFID) is the technology at work inside every electronic tag. What makes a superior tag is a combination of quality components and great design. Shearwell SET EID tags are always the right choice – tough, tested and trusted. (SET stands for Shearwell Electronic Tag.)


What’s inside?

Every electronic tag contains a transponder - a microchip and a coil of copper wire which acts as an antenna. The microchip is pre-programmed at Shearwell with a unique code that is assigned to the animal when it is tagged.


SET Strip
SET Transponder
SET Closed

 The transponders in Shearwell SET tags are low frequency and are inserted into a cavity in the body of the tag. This location protects the transponder from any pressure or damage. After insertion the tag is sealed to lock the transponder in place. The visual number is then laser printed on the outside of the tag. Where the visual number differs from the microchip number, the correlation is stored at Shearwell and can be supplied to the customer.

Empty SET tags
 Transponders Inserted
Tags Sealed

The transponder in a button tag is built inside the female part. The antenna circles the centre hub and is over-moulded with plastic to protect it from moisture and damage.

Underside of female button
Button Tag

Better by design 

 An ear tag is designed to survive some harsh treatment; it gets hot, cold, wet, frozen, bitten, pulled, scraped and squeezed - whatever the ear endures the tag must too.

The challenge is to keep the electronics safe, not just from the weather and animals but from the application process itself.

A one-piece EID tag is quite a feat of engineering – the plastic must be flexible enough to bend without breaking, rigid enough to punch a hole through a sinewy old ear, tough enough to protect the electronics inside, plus small and light enough for a newborn lamb to carry.

 A tag undergoes the most stress and strain as it’s being snapped into the ear.
Applicator Jaws

Two-piece tags have a harder grade of plastic in the spike than in the rest of the tag, making this design more suitable for older animals with tougher ears.

Button Spike

Tag Retention

The consequences of losing a tag can be serious so it's important that tag retention is as good as possible.

Tag retention is influenced by:

  • Correct placement in the ear
  • Ensuring the male and female parts of the tag lock together properly
  • Infection – affected by cleanliness, flies, flock/herd health
  • Environmental hazards – twine, wire, fence and feeder design

The size of the puncture hole can also affect the retention rates between different kinds of tags. Loop tags such as the SET tag experience very little movement if properly positioned in the ear, and are unlikely to snag on wire, twine or net.


 Tagged Sheep

Tag Reading

Low Frequency RFID tags have no internal power source such as a battery. Instead the microchip in the tag is energized by the radio frequency of the tag reader. The electrical current is very small but just strong enough to power up the microchip to transmit the ID number stored back to the reader.


Several factors affect the read range of an electronic tag.

  • How the reader is powered.
  • Size and type of antenna used.
  • Competition from other devices emitting electrical interference. Fluorescent lights and electrical motors running nearby can interfere with the radio signals between the tag and the tag reader. Metal panels and loops of metal can also affect the performance of panel readers.


According to the International Standards - ISO 11874/11875 - two technologies can be used for animal identification. These are FDX (Full Duplex) and HDX (Half Duplex). ISO compliant readers will read both. The difference is in how the microchip is energized by the reader. FDX transponders receive and transmit simultaneously while HDX transponders receive and transmit separately. 


Radio Frequency

Low frequency tags are used for animal identification around the world. The ISO standards for EID are set by international committees, and all EID tags sold in the UK must conform to the standards. High frequency or ultra-high frequency tags are not currently approved for use in livestock.


What's Next?

We are constantly exploring new technology and its possible benefits for animal identification. Working closely with our customers, as well as statutory, commercial and industry partners, helps to drive us forward with ever better management solutions to help the livestock farmer.