In Germany for example the regulation BGV B11 has to be applied. The safe operation of demagnetizers requires the observance of exposure limits!. Workplaces must be checked for compliance with the regulations of the employers’ liability insurance associations BGV B The measurements or calculations. Health and Safety Regulation on electromagnetic fields (EMFV); The health and safety requirements of the employers’ liability insurance association BGV B
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Despite this, a significant overestimation cannot be excluded either. The magnitude of s t on excitation with an impulse with amplitude 1 mT. When displayed in log-log graphs, this gives piecewise linear reference-level curves. Wideband sensors and test antennae with spectral analysers are available. This would at least be true if the amplifiers and AD converters are equivalent and the field probes used are equally sensitive.
The disadvantages of competing methods bgb demonstrated. Modal analysis and operational vibration. This is because the permissible field quantity swing has been set too high by a factor of 2. However, there is no justification for this underestimation based on physical or biological grounds.
A weighted time signal s t is available at the output of the weighting filter. Strategic environmental impact assessments.
In contrast, b11 that can be formed from a cascade of first order filter elements emulate the underlying effects much more realistically. Dynamic stiffness of elastic elements.
However, the ensuing measurement deviations in some high quality commercially available measurement systems are so small that b11 can be neglected in practice. All measuring devices have traceable calibration and are subject to in-house test equipment monitoring. The filtered signal is normalized to e 0. Workplaces must be checked for compliance with the regulations of the employers’ liability insurance associations BGV B Because BGM is worded very intricately and only covers specific examples, eqn 26 is naturally ggv an exact description of BGM.
Measurement systems for non-thermal effects that already digitize g t unfortunately show a much lower dynamic range. It is therefore clear that the field quantity swing relevant to stimulation is the peak value and not the peak-to-peak value of the field characteristic. The sampling frequency of the digital filter must be chosen much higher than 3 kHz, however, so that the analog high pass filter with 3 kHz cutoff frequency can be approximated without any significant deviations.
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It is also still identical to the first order high pass filter at the start but shows strong oscillations and decays much more slowly. Quite the opposite is the case. If g t actually consists only of segments that correspond exactly to these four curve forms, BGM can be used. BGM gives a correct assessment for signal segments with a field change of the form ; and.
The DC component must be assessed separately.
However, it is actually the ggv that the rule for the field quantity swing only applies to field characteristics free of DC components and then only for field b1 swings within the same sign. The parameter k in eqn 8 represents a coupling factor. The isotropic variant of WPM is then calculated as follows: A time frame of 5 ms was transformed for Fig. If the value of 1. If W f can be described by first order filter elements, the filter with the lowest b1 frequency largely determines the length of the impulse response.
Weighting then takes bfv in the frequency domain by multiplication with W f. Arts, Culture and Events. If rectangular direct current DC impulses are used as an internal electrical field strength stimulus, a stimulation effect does not occur until the amplitude of the internal field strength exceeds the threshold value e T.
A minimum phase system is assumed. The solutions used in state-of-the-art equipment have been demonstrated. The following filter made up from a cascade of first order filters is a very vgv approximation for the reference levels of the Low ALs for magnetic flux density:.
Finally, S f is transformed back into the time domain. Isotropic probes capture all three orthogonal field components simultaneously. Correct conclusions made for high frequencies and short times are wrongfully applied to low frequencies and long times.
Berufsgenossenschaft der Feinmechanik und Elektrotechnik. Footnotes The author declares no conflicts of interest.
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The first measurement system available with STD had precisely this structure. Nevertheless, it does make the effect of V max quite clear and shows what BGM does in principle, as well as how BGM could be expanded to cover any field characteristic mathematically exactly and unambiguously. In cases where T i is greater than 1 s, T i is set equal to 1 s.
Such filters are also called RC filters. The assessment is correct at high frequencies. The artifacts that clearly occur in the red curve depicted in Fig.
Electromagnetic environmental compatibility
In practice, it has been shown that field generators that are designed to generate very high direct currents also generate significant AC components.
To eliminate this effect initially, the frequency f p of the field quantity change bfv investigated in two regions:. The phase response of a minimum phase system g11 known to be equal to the imaginary part of the Hilbert transform bggv the natural logarithm of the magnitude response.
As already described, W f for WPM should always be defined by a cascade of first-order filter elements. So far, WPM has only been described for one field component. The permissible amplitude of the sinusoidal signal is now higher by the factor Vbut the permissible RMS value of the pulsed signal remains the same as that of the non-pulsed signal.