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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:36 |
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Conference: Bucharest University Faculty of Physics 2003 Meeting
Section: Electricity and Biophysics
Title:
Measuring gauge for the strengh of the electromagnetic field
Authors:
Adrian RADU, Liviu GIURGIU
Affiliation:
lgiurgiu@hades.ro, adrian-radu@fpce1.fizica.unibuc.ro
University of Bucharest, Faculty of Physics, PO Box MG-11, 76900 Bucharest, Romania
E-mail
Keywords:
Abstract:
The contribution presents a new device which is intended to measuring the intensity
of the electromagnetic field in the range of 525-1605 KHz and 88-108 MHz.
The necessity of making such a device has been raised by the need of
determining of the shielding factor of some covers used in protecting equipment
from the electromagnetic filed.
For the two frequency ranges, the magnetic component of the electromagnetic field
is detected by two probes of magnetic antenna types.
The electrical signal yielded by the probes, which is amplified and mixed by a heterodyne stage,
is converted to a fixed intermediate frequency.
This signal is amplified to such a level that allows its demodulation.
The strength of the radiofrequency field is measured by means of an integrated circuit BM3189,
which was originally designed as an FM receiver.
In our applcation is only used as amplifier-demodulator. Its DC output voltage
is proportional with the logarithm of the input voltage level.
The output signals for the two ranges are balanced by means of op amps included
in a general purpose IC, namely BM324. Finally, the output of the DC op amp is fed
into a measuring instrument, which is logarithmically calibrated.
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