Executive Summary
A study was carried out to investigate the effects of electromagnetic interference ( EMI) in transceivers used to identify animals electronically, commonly known as RF identification ( RFID) or electronic identification ( EID). This study was commissioned by Scottish Executive Environment and Rural Affairs Department, SEERAD, as part of the ongoing project aimed at providing an advanced and highly efficient electronic cattle traceability system using EID and supported by EDT (e-Delivery Team) that was later extended to include sheep.
Various UK manufacturers were contacted with the intention of obtaining samples of RFID tag readers for the laboratory EMC testing. It was clearly anticipated that manufacturers would be eager to have the EMC performance of their equipment assessed or re-assessed, especially since the testing was offered at no cost to the various manufacturers. Unfortunately, there was a lack of response from most, which was extremely disappointing and somewhat limited the laboratory study to the manufacturers who kindly offered their equipment for testing. Large amount of time and effort was concentrated in generating the interest in this study, but most manufacturers were simply not willing to participate in the investigation.
Research into the current knowledge of RFID systems found much about the theory and implementation of such systems but very little on any studies into the effects of EMI on the ability of these systems to operate under adverse electromagnetic conditions.
To determine what levels of EMI were likely to be present at locations where these EID systems would be used, radio frequency measurements were performed and recorded at a selection of sites during normal working conditions in order to compare actual EMI levels on site with the immunity levels normally required for compliance of equipment to the EUEMC Directive.
The sites chosen for these measurements were auction marts and abattoirs in Scotland since they are the places where major movements of livestock occur. At present, these sites use standard visual ear tags as identification, matching the tags with the animal 'passports' and manually recording the data prior to transfer to central recording.
A brief visual survey of the auction marts did not reveal any major sources of EMI, and this was borne out by analysis of the recorded data. Typically the main sources of radio frequency emissions noted were local broadcast transmissions, e.g. radio, television and mobile telephone base stations.
The abattoir environment was found to more electromagnetically noisy. At the stunning areas, cattle and sheep, there were various sources of EMI such as conveyors, stunning equipment, hoists and processing equipment. These produced significant amounts of RF interference as both conducted (onto power cables) and radiated.
Samples of RFID tag readers, panel antenna type and hand held stick type, were also obtained for laboratory testing, where they could be subjected to EMI under controlled conditions. These tag readers were compliant to the ISO 11784/11785 standards, operating at 132.4 kHz and reading both full and half duplex ( FDX and HDX) tags. In addition to testing to the requirements of applicable EMC standards for immunity, the levels and frequency ranges of the EMI could be varied to examine the effects on the reader systems.
The results of the laboratory studies showed that the panel tag readers tested were susceptible to both radiated and conducted RF interference to the extent that they would require some mitigating modifications to make them fully compliant to the EMC requirements. They were particularly susceptible to conducted RF interference in the range 150 kHz to 230 kHz. Varying the frequency range showed the susceptibility extended down to at least 10 kHz. Increasing the applied disturbance to the next higher level increased the frequency range of the immunity effects to 288 kHz.
The laboratory studies indicate that the manufacturers should ensure that their equipment is, at a minimum, compliant to the requirements of EN 301 389-1 this is an RTTE standard. All equipment of this type should be, since compliance to the EUEMC Directive is a legal requirement. If the equipment is to be installed in an electromagnetically severe environment or close to equipment that is a known source of EMI, then manufacturers should introduce measures in either or both manufacture of the equipment and installation of the equipment to mitigate the effects of any local EMI.
To this end a Guideline for Build and Installation manual has been compiled outlining steps that can be taken to reduce the effects of EMI on both manufactured and installed equipment, through good design and careful installation.