The hazard potential of magnetic fields at the workplace is relatively difficult for workers to determine, since the fields are not visible. In case safety distances are not clearly marked, it might be difficult to adhere to safety arrangements, e.g. for persons fitted with cardiac pacemakers. Visualization of the fields can provide a better understanding of the exposure situation and thus improve workplace safety.
In practice however, creating sketches (for example) often proves time-consuming, and the two-dimensional representation is not always readily comprehensible. The aim of the AURA project (augmented reality measurement system for magnetic fields) is therefore to use augmented reality technology to display measurements of magnetic flux densities directly in a smartphone's video display. Images and videos of the workplace onto which the measured fields and the required safety distances are projected can be made available to the workers following measurement. This enables the workers to understand the exposure situation easily and assess where they can work safely. The system could also be used in training courses and seminars in order to present exposure situations illustratively and in context.
Video: AURA in an example in the field (non-accessible format)
The video shows the results of a master's thesis carried out as part of the AURA project. A smartphone is connected to a measuring device for magnetic fields and the video image of the smartphone spatially correctly shows recorded measurements at a resistance welding system. The measured values are visualised as colour-coded spheres, with the colours (green to red) indicating whether permissible values according to a selected set of rules have been exceeded. The augmented reality technology of the smartphone makes it possible to change the position of the smartphone while the measured values in the video image continue to be displayed at the correct position in the room. Safety distances to be observed are visualised in an easily understandable way by means of a square and the scene can be viewed simultaneously from a different perspective with a second smartphone. An investigation showed that the understanding of the exposure situation is improved by AURA images.
Low-frequency magnetic fields emitted by certain equipment may cause irritation of the nervous system in workers. The provisions in the OSH Ordinance on electromagnetic fields (EMFV) of the German Federal Ministry of Labour and Social Affairs (BMAS) present a protection concept that prevents such irritation. The EMFV states the weighted peak method (WPM) or other state-of-the-art methods for the assessment of pulsed fields. The time-domain assessment method (TDA) has been used in Germany for many years for occupational health and safety purposes. The two methods, WPM and TDA are based on slightly different assumptions regarding the underlying physiology of nerve stimulation, and in some cases yield divergent assessment results. Therefore, it might prove difficult to reach an informed and reliable decision using these methods in certain scenarios. The issue is being addressed jointly by the Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA) and the German Social Accident Insurance Institution for the woodworking and metalworking industries (BGHM).
The possible interference with active implants (specifically cardiac pacemakers and implantable cardioverter-defibrillators, ICDs) caused by electronic article surveillance systems used in the retail trade (radio-frequency identification systems, RFIDs) was studied at the request of the German Social Accident Insurance Institution for the trade and distribution industry (BGHW). Several measurements were conducted on site in order to record the workers' exposure. RFID systems with operating frequencies in both the low-frequency and high-frequency ranges were studied. Besides evaluation of the exposure for all workers in accordance with DGUV Regulation 15, the fields arising were evaluated for possible interference for workers fitted with an active cardiac implant.
The project studied the exposure of persons fitted with cardiac pacemakers or defibrillators in the close field of a high-frequency electromagnetic field (f > 16.9 MHz). The electric voltages induced on the input to the implant were determined for a range of exposure scenarios by field simulation calculations with the use of a digital body model including implant. From this, a procedure was then developed for estimation of the voltage generated on the input to the implant based upon the power density measured in the near field of the antenna. The action limits for the mean power density were included in the analyses in accordance with the German Ordinance on protection of workers against hazards presented by electromagnetic fields (EMFV), Table A3.4.
In the project concerning electromagnetic fields on manually guided medium-frequency/inverter-based spot-welding machines, the distribution of the magnetic field and the effects of this field were analysed and visualized in a body model on welding tongs of varying electrode interval and geometry. The results were visualized for selected levels of the body (trunk, neck, head), compared with the values in the guidelines of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) for low-frequency magnetic fields, and evaluated.
Before persons who have been fitted with active implants can return to their workplaces, it must be determined whether the function of the implants could be disrupted by electric, magnetic or electromagnetic fields in the working environment. For many tasks, this is not considered an issue. It is however critical for work involving manually guided electric tools such as power drills, circular saws, jig saws and manual routers. Observance of a safety distance of up to 40 cm from the tools is therefore recommended in such cases. Experience has shown observance of such a great distance to be unrealistic in practice.
The project was to examine systematically the levels of the fields emitted by manually guided electric tools as a function of the power supply (mains, battery) and the potential influence of these levels upon implants in the human body. A mathematical model was to be used to calculate the disruptive voltages induced on the input of an implant. This model employs a body model in which the arrangement of the tissue structures corresponds to the human anatomy. The objective was to use the results to formulate practical measures for the protection of persons fitted with implants during work involving manually guided electric tools.
In the project described here, exposure arising during tasks involving hand-held spot-welding guns with separate 50 Hz AC power supplies was assessed for the first time with reference not only to results of workplace measurements, but also to calculated current densities in the human body. Current densities were analysed, visualized and finally evaluated in a three-dimensional field simulation in multiple layers of the human body for frequently occurring work situations.
Accident Prevention: Digitalisation - TechnologiesTel: +4930 13001-3580
Accident Prevention: Digitalisation - TechnologiesTel: +49 30 13001-3581
Accident Prevention: Digitalisation - New TechnologiesTel: +49 30 13001-3583