Specifications

B-field Exposure From Induction Cooking Appliances 23
Spherical isotropy The experimental setup shown in Figure 15 f) was used to evaluate the
spherical isotropy of the Narda probe ELT-400. The probe rotates around its vertical z-axis,
and the B-field is measured as a function of the probe angle of rotation (from -180
◦
to 180
◦
).
The measurements are performed on the top and at the side of the Helmholtz coil (see Figure
15 e) ). The uncertainty due to deviations from spherical uncertainty has been determined by
the worst-case values assuming rectangular distribution, i.e., ± 0.2 dB/
√
3.
Linearity In order to check the linearity of the probe, a sinusoidal voltage was applied to the
Helmholtz coil, with the amplitude varying between 0.1 V
pp
and 10 V
pp
(frequency of 20 kHz).
The experimental setup shown in Figure 15 f) was used. The probe was centered in the Helmholtz
coil. The B-field was measured as a function of the voltage applied to the coil as shown in Figure
16. The linearity is very good for B-fields greater than 0.3 µT, which corresponds to a deviation
from linear response < ±0.05 dB. The error increases for lower fields and equals 2.8 dB for
B-fields of ≈ 0.06 µT (0.1 V
pp
).
Figure 16: Linearity of the Narda probe ELT-400. a) The B-field is measured for amplitudes
between 0.1 V
pp
and 10 V
pp
(frequency 20 kHz). b) Deviation from linear response in [dB].