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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All currently known commercial measuring devices that use WPM only operate in the time domain using first order filter bfv and reliably deliver the correct results. FEM model updating and optimisation.
The same W f is used. This would at least be true if the amplifiers and Bv converters are equivalent and the field probes used are equally sensitive. It is therefore clear that bfv field quantity swing relevant to stimulation is the peak value and not the peak-to-peak value of the field characteristic.
To eliminate this effect initially, the frequency f p of the field quantity change is investigated in two regions:. No appreciable errors occur if all three of the following conditions are concurrently met:. The weighting filter W f must have the inverse frequency response of and is therefore given by:.
Measurement systems for non-thermal effects that already digitize g t hgv show a much lower dynamic range. The maximum overestimation for sinusoidal signals is by a factor of and occurs precisely at a frequency of 3 kHz. Thus, BGM can only be used in such cases if a significant underestimation is taken into account. DFT is also based on a sampled time signal rather than a continuous time signal. Emulation of the sharp edges of R f should not therefore be pursued because artifacts occur that lead to erroneous estimation of the exposure index.
The finite transformation length T of the DFT can lead to incorrect assessments in practice. Flow resistance measuring system.
The phase can therefore be calculated from the magnitude: Thus, the usual W f that emulates the underlying physical and biological effects accurately, and can be realized using first order filter elements, is not always used. A minimum phase system is assumed.
The method can be used without limitations for any field profile and emulates the underlying physical and biological effects significantly better than all other presently known methods. Thus, V is unity, and the sinusoidal signal must meet the normal reference levels.
The assessment is correct at high frequencies.
All measurement systems have intrinsic noise. Find articles by Helmut Keller. Rueckerl C, Eichhorn Hgv.
Because the reference levels are very strongly dependent on frequency, the dynamic range of measurement systems [that digitize s t instead of g t ] is bfv larger.
Berufsgenossenschaft der Feinmechanik und Elektrotechnik. The same is true for the use of the weighted RMS value with an integration time of 1 s. However, the artifacts here h11 even more pronounced, leading to an even larger underestimation by a factor of 0.
Quite the contrary is the case, because the fundamental physical and biological effects are actually much more exactly emulated by first-order filter elements. However, they are 12 times lower in the frequency range from 8 Hz to 25 Hz.
This normalized stimulation signal is exactly the magnitude of s t in WPM.
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Limiting V to V max is justified by an alleged but otherwise unexplained safety risk with very short pulses. Measurements of electromagnetic fields can be performed across the entire frequency range between 0 Hz static field and 40 GHz. A time frame of 5 ms was transformed for Fig. Assessment of hazardous substances. The parameter k in eqn 8 represents a coupling factor. The weighting filter convolves the field quantity g t with an impulse response w twhere w t is the inverse Fourier transform of W f: There is a noticeable sustained oscillation at a frequency of approximately 3 kHz, which slowly rises and falls in amplitude and which has maximum amplitude but negative sign at about the same time as the step occurs.
The magnitude of s t on excitation with an impulse with amplitude 1 mT. The peculiarities that need to be taken into account when applying WPM in the frequency domain are therefore not discussed until later in this article. The maximum value of s t is only 0.
Electromagnetic environmental compatibility
In particular, WPM in the time domain can be used without a second thought. However, WPM is also used in the frequency domain with a W f that closely approximates the sharp edges of the piecewise linear reference curves using very high order filters.
This factor lies between unity and V max and depends on the crest factor of the signal.