1 Conclusions of the Overall Study
The following conclusions can be drawn based on the results obtained during this project:
1.1 Desk Based Research - Report 2433CR1 - Appendix 1
The report, document number 2433CR1 (Appendix 1) summarises the findings of a desk based research into the subject of acoustic and mechanical vibration and other physical effects on the performance of electronic ID tagging in animals. As detailed in the report, the work performed in this area is extremely limited in both academic research and detailed studies. The limited information available clearly identify that metallic structures affect the functional operation of RFID systems, but without providing any detailed explanation.
1.2 Procurement of RFID Systems for the Study
Various manufacturers and distributors were approached to participate in this study. Only a total numbers of 4 samples could be procured for this study and these samples were obtained from 2 independent distributor/manufacturers.
Test samples were extremely difficult to be procured and manufacturers and distributors were, in general, not interested to participate with this work, despite the clear potential benefits (testing and characterisation of their units, gained experience...).
1.3 Study of Acoustic Interference - Report B179CR1 - Appendix 2
Acoustic conditions in auction markets and abattoirs give rise to short duration bursts of high intensity sound, resulting from steel gates and impacts against steel barriers. This has considerable high frequency content, extending into the ultrasonic range.
Loud sounds were found to affect tag reader systems such that their performance is degraded or completely inhibited. Samples 3 and 4 were affected by sound interference during testing, for both frequency swept measurements (Frequency domain) and impulse measurements (time domain).
For samples 3 and 4, susceptibility occurred at low frequencies, in the order of a few hundred Hertz, and with relatively high levels of sound applied, and also between 25 and 40kHz with 0dBPa applied, and at 80kHz at a relatively low level of -20dBPa. For both these samples, high levels of degradation of performance were measured (ranging from 25 % to 94%).
It is possible to manufacture tag reader systems such that they are immune to sounds of the levels likely to be encountered in auction markets and abattoirs. Samples 1 and 2 were not affected by any levels of sound applied during testing including some additional extra high levels at spot frequencies.
1.4 Study of Vibration Interference - Report 100802TR1 - Appendix 3
The mechanical environment in auction markets and abattoirs consists of random vibration of a moderate level with short duration, but frequent, bursts of high acceleration shock, resulting from steel gates, impacts against steel barriers, operation of machinery and animal movements.
The levels of vibration measured varied from site to site but were typically in the range between 2g and 10g RMS, although at times levels considerably in excess of this could be experienced for short periods.
The high level shocks present were typically of short duration (<1ms) but could have amplitudes from 50g to as high as 500g dependent upon the mechanical configuration of the site.
The variation between sites of the level of mechanical vibration and shock measured indicate that considerable care will need to be taken in selecting a location in which to install RFID reader systems.
It is possible for vibration and shock to affect tag reader systems such that their performance is degraded or completely inhibited. All samples were affected by vibration and shock during testing, with degradation varying substantially between samples. The level of vibration at which these effects start to occur is typically less than 1g RMS, and so is well within the envelope of conditions likely to be encountered in auction markets and abattoirs.
All samples tested were sensitive to shocks of the type found in auction marts and abattoirs and exhibited degraded performance under these conditions, ranging from 88% to 64% of full performance.
All readers tested recovered fully and automatically on removal of vibration and shock.
There was significant variation in performance between the four reader systems tested. The best, Sample 1, operated at levels as much as ten times higher than the levels at which the other readers ceased to function.
The readers have clear sensitivity to stimulation of their inherent mechanical modes of vibration. Within the scope of this study it was not possible to fully explore the nature of this sensitivity but further work in this area would help in understanding the potential problems that will be faced by trying to install and operate these kinds of systems in environments such as abattoirs and auction markets.
The site measurements made demonstrate that random vibration is a more realistic form of stimulus to be used to validate operational performance of reader systems than sinusoidal vibration.
Three of the readers were extremely sensitive to the proximity of metal that could readily disrupt their function. This sensitivity was not confined to magnetic materials as they appeared also to be affected by materials such as aluminium alloy.
1.5 Study of Modulation/Metallic Interference - Report 2527CR1 - Appendix 4
Four RFID systems have been assessed for their physical performance when used in a non-metallic and metallic environment. The following specific studies have been performed:
1. Characterisation of the magnetic field distribution in X, Y and Z-axes (magnetic field axes)
2. The maximum distance for tag readability
3. The bandwidth at the magnetic field frequency (134.2kHz) and the derivation of its Q-factor
4. The effect of the number of tags within the field at any one time.
The first study shows show that each case, the magnetic field amplitude of all four samples is affected when the antenna is mounted on the kiosk. Sample 1 magnetic field amplitude was reduced by approximately 30%, sample 2 by approximately 40%, sample 3 by 70 to 80% and finally sample 4 by 70 to 80%.
In addition, all of the three-dimensional plots indicate distortion of the field to some extent due to the presence of the metal kiosk.
The measurements show that there are slight variations in the magnetic field around the centre line but generally the field produced by each of the sample appears quite planar within the limited area of measurement, thus contributing to consistent tag reading within that area.
The second study shows that the effect of the kiosk on the tag read distance was significant in all samples but extreme in Samples 3 and 4 to the extent that no significant read distance could be obtained.
The third study shows that the presence of metal has little effect to the Q factor of the RFID system. Theoretical analysis supports this conclusion.
The fourth study shows that for Sample 1 and 2, there appears to be a maximum read number of 6 individual tags at any pass. The effect of the kiosk was to reduce the ability of the antennae to read the tags primarily due to the reduction in the amplitude of the magnetic field.
Similarly with Samples 3 and 4, there appears to be a maximum read number of 4 individual tags at any pass. The kiosk reduced the amplitude of the magnetic field to such an extent that no read was obtainable at the test distance.
1.6 Code of Practice
During the meeting between the representative of York EMC Services (2007) Ltd ( YES ltd) and Scottish Government on 20th March 2008, it was agreed by the project steering committee that the results obtained during the research could not be developed into a Code of Practice for the use of EID systems in markets and abattoirs as specified in the contract.
The results required to develop a Code of Practice were not obtained due to the build quality standard of the commercially available equipment that was under investigation, and not in any way related to the scientific quality of the work carried out by YES Ltd. In light of this the steering committee agreed that YES Ltd should not be bound to produce a Code of Practice.
Further research will be required to validate engineering concepts in order to propose suitable mitigation measure