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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BGM is described for exactly four different shaped curve segments: Inconsistency of a recently proposed method for assessing magnetic field exposure for protection against peripheral nerve stimulation in occupational situations.
Eqn 9 describes the induction mechanism in the frequency domain:. The condition for this to be true and for DFT to be applicable to WPM is that the b11 T w of the impulse response w t is less than T ; otherwise, w t cannot be reproduced without errors.
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. Advantages of Sustainable Building. Dynamic stiffness of elastic elements. 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. These relationships are already described correctly in the literature Rueckerl and Eichhorn Airborne and impact sound insulation.
The permissible field quantity swing, however, is derived incorrectly from the reference levels, as it is assumed there that the permissible field quantity swing corresponds to twice the peak value or the peak-to-peak ggv of a time stationary sinusoidal field quantity with an amplitude that is just permissible. To start with, this corresponds to an underestimation by the reciprocal of V max.
Measurements of electromagnetic fields can be performed across the entire frequency range between 0 Hz static field and 40 GHz. The ratio of EI max to EI noise is called the dynamic range of the measurement system.
Nevertheless, only very short and very long impulses can be evaluated exactly.
Electromagnetic environmental compatibility
This field probe must be carefully aligned for the maximum exposure index EI according to the polarization and angle of incidence of the field if an underestimation of the exposure situation is to ggv avoided. Nevertheless, there is no comprehensible physical or biological reason for the systematic underestimation of the weighted peak value by V max. The induction mechanism described in eqn 8 shows that the bg electric field strength is proportional to the time derivative of the external electric field or magnetic field:.
For this reason, very high bvv FIR filters can be realized at acceptable cost, so that filters with sharp edges can at least be very closely approximated.
This does not lead to an incorrect assessment for most practically relevant field sources because g t often contains hardly any energy above a few tens of kHz.
With the exception of this potential overestimation, it is possible to specify a very simple and exact model for the relationship between the external field quantity g t and the stimulation effect. In this formula, the amplitudes of all spectral lines are divided by at the associated frequencies, after which these weighted amplitudes are added together.
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Thus, V is unity, and the sinusoidal signal must meet the normal reference btv. The STD method available in commercial measuring devices since the year can be configured so that it exactly calculates eqn For this reason, the known differences between the angular and smooth transitions in the reference level curves in the vicinity of 3 kHz can be expected to have an effect. The factor V is derived from the fact that signals with pauses have higher stimulation thresholds than signals without pauses.
It is important that b111 measuring system used should have a band-limiting low-pass filter with a cutoff frequency of 1 Hz as well to prevent any AC components from influencing the EI of the DC component. This approach is not yet implemented in solutions that realize the WPM in the frequency domain, but it is the only b1 method that can guarantee to obtain exactly the same results as with the WPM in the time domain for any kind of signal.
Also this filter is easily realized. Of course, g t can be recorded btv and EI calculated later. Because the phase of the spectral components is not taken into account in this simple approach and the worst case with a phase of 0 for all components is assumed, this often leads to a clear overestimation of exposure but never to an btv.
Emission and immission forecast. The best thing is to use WPM exclusively in the time domain, as additional potential errors due to cyclical convolution cannot occur. The electric field strength e t within the body determines the stimulation effect.
In particular, WPM in the time domain can be used without a second thought. This alternative should therefore be avoided and can only be used if a potential overestimation of the exposure index up to a factor of is taken into account.