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【正文】 ransfer function A Filter Bx Sensorcoil x Square Transfer function A Filter By Sensorcoil y Square + Average √ . Transfer function A Filter Bz Sensorcoil z Square Figure Z2 Schematic diagram of the reference method NOTE Different ways that the transfer function can be applied to a time domain signal include: analog filter in an electronic circuit, preprogrammed DSP chip, a signal analyser, or a digital puter calculation with a spreadsheet package or a customwritten program.~ – 11 – BS EN 62233:2020 }The actual measured value shall be pared directly with the reference level BRL of the flux density at 50 Hz. With appliances with highly localized fields, this has to be performed after taking the coupling factor ac(r1) given in Annex C into account. The final weighted result, W, can be derived as follows: or applying the coupling factor ac(r1) W n ?? B . B RL W nc ? a c ( r1).Wn where Wn weighted result for one measurement。 . value of the magic flux density。 BRL reference level of the magic flux density at fC0。 ac(r1) coupling factor according to Annex C or Table . Wnc weighted result for one measurement taking the coupling of the inhomogeneous field into account by applying ac(r1). The determined weighted result W shall not exceed the value 1.~ Line spectrum evaluation This method may be used when there is only a line spectrum, for example for magic fields having a fundamental frequency 50 Hz and some harmonics. See Clause 4. The magic flux density is measured at each relevant frequency. This can be achieved by recording the time signal of the flux density and using a Fourier transformation for evaluating the spectral ponents. The following sequence is used for the measurements: ? perform a separate measurement of each coil signal (x, y, z)。 ? integrate the signals to get a value which is directly proportional to B(t)。 ? perform a discrete Fourier transform for each coil to obtain the estimated discrete magnitude spectrum B(i) representing values at the discrete frequencies f(i) = i / T0. (T0 = observation time)。 ? find the local maxima with B(j) at frequency f(j) by interpolating the discrete spectrum B(i)。 ? perform a vector addition of all three directions for every discrete spectral line B(j). B( j ) ?? B 2 ( j ) ? B 2 ( j ) ? B 2 ( j ) (4) x y z NOTE The last two operations of the algorithm can be interchanged by using Equation (4) with B(i) instead of B(j). Result is the amount of the magic flux density for each detected frequency. To pare the measured values with limits, the reference level BRL(j) must be used. For appliances with highly localised fields the coupling factor ac(r1) given in Annex C can be taken into account. For fields with several frequency proportions the calculation of a frequency weighted sum is necessary. The weighted result is obtained from the following formula: n ? B( j ) ? 2 Wn ?? ? ? B ??( j ) (5) j?1 ? RL ??BS EN 62233:2020 – 12 – ??or applying the coupling factor ac(r1): Wnc ? ac (r1 ) ? Wn (6) NOTE Coupling factor can be independent of frequency, for details see Annex C B(j): magic flux density at the order of j frequency line of the measured spectrum BRL(j): reference level of the magic flux density at the order of j frequency. ac(r1): coupling factor according to Annex C or Table . Wn: weighted result for one measurement. Wnc: weighted result for one measurement taking the coupling of the inhomogeneous field into account by applying ac(r1) The determined weighted W shall not exceed the value 1. }Text deleted~ NOTE A pure summation always results in an overestimation of the exposure and for broadband fields consisting of higher frequencies harmonic ponents or noise, the limitation based on summation formula is very conservative because the amplitudes are not in the same phase. W ith most measurement equipment the relative phases are not measured (for example if a spectrum analyser is used), but an rms summation of frequency ponents can be undertaken. This will usually give a more realistic oute than neglecting phase pletely. } Simplified test methods Appliances that are constructed so that they can only produce magic fields at mains frequency and its harmonics need only be tested in the frequency range below 2 kHz. Appliances are considered to meet the requirements of this standard when all the following conditions are fulfilled: ? the currents, including the harmonic currents, generating the magic fields are known。 ? all harmonic currents with amplitudes higher than 10 % of the amplitude of the mains frequency decrease continuously over the frequency range。 ? the magic flux density measured at mains frequency is less than 50 % of the reference level specified for the mains frequency。 ? the magic flux density measured during a broadband measurement over the frequency range, with the mains frequency suppressed, is less than 15 % of the reference level specified for the mains frequency. NOTE An active notch filter is a suitable means for suppressing the mains frequency. If the conditions are not fulfilled another measurement according to the reference method is remended. Appliances that are constructed so that they only produce very weak magic fields, when the mains frequency is dominating, are considered to meet the requirements of this standard when all the following conditions are fulfilled: ? the currents, including the harmonic currents, generating the magic fields are known。 ? all harmonic currents with amplitudes higher than 10 % of the amplitude of the mains frequency decrease continuously