In this live-streamed exercise in the "Electromagnetic Compatibility" module, we are discussing the solution of task 14 of our exericse booklet on field impedance.
At a distance of 1m in front of the screen surface of a monitor, an electric field strength with a level of L_E = 83 dB(µV/m) at 22.5 kHz (horizontal scan rate of a cathode-ray tube display) has been measured.
How large is the magnetic field strength if the source is assumed to be
a) an electric interference source or
b) a magnetic interference source?
print version: https://cloud.ovgu.de/s/PTfXwD74kwbYaYM
smartphone version: https://cloud.ovgu.de/s/KKoQeBJdimFzwWg
https://cloud.ovgu.de/s/rmDBzgykbsEdkeS
https://cloud.ovgu.de/s/3pmRfPM4QotKRod
clear all
clc
L_E=83
f=22.5e3
E=10^(L_E/20)1e-6
E1e3
c=3e8
lambda=c/f
lambda/1e3
r_0=lambda/2/pi
eta_0=377
r=1
eta_electric=eta_0r_0/r
eta_electric/1e3
H_electric=E/eta_electric
H_electric1e9
eta_magnetic=eta_0r/r_0
H_magnetic=E/eta_magnetic
L_H_electric=20log10(H_electric/1e-6)
L_H_magnetic=20log10(H_magnetic/1e-6)
L_eta_electric=20log10(eta_electric/1)
L_eta_magnetic=20*log10(eta_magnetic/1)
L_E-L_eta_electric
00:00 Welcome and explanation of the task
02:29 Conversion of the level into a field strength
07:49 Field impedance
16:23 Calculation in GNU Octave
26:34 Practical aspects
29:17 Calculation with levels in dB
44:30 Discussion of the dB calculation