BRUEL & KJAER 4188 - Effect of Magnetic Fields; Electromagnetic Compatibility (EMC)

Chapter 8 —
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" Microphone Preamplifier Type 2669
Effect of Magnetic Fields
Falcon™ Range of Microphone Products
Microphone Handbook
BE1380– 12
8
−
9
8.6 Effect of Magnetic Fields
Typically <3µV for 80A/m at 50Hz
8.7 Electromagnetic Compatibility (EMC)
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" Microphone Preamplifier Type 2669 is constructed such that it is extremely
resistant to external electromagnetic radiation. This is important when measuring
near such things as radar and radio transmitters (for example, mobile telephones).
An important prerequisite for acheiving this immunity is that connected instrumen-
tation also fulfil these requirements and that the preamplifier’s termination in the
measuring instrument is correctly constructed (see Fig.8.10). Brüel&Kjær equip-
ment which are designed for connection with
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" Microphone Preamplifier Type
2669L and the supplied extension cable fulfil the requirements for immunity to
external electromagnetic radiation.
Note:
Brüel&Kjær equipment, typically those having the traditional Brüel&Kjær
microphone socket, do not fulfil these strict immunity reqirements.
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" Microphone Preamplifier Type 2669 conforms to EMC requirements EN50081–1
and prEN50081–2 when connected to an instrument that also conforms to these
regulations.
Fig.8.10 Simplifed electronic construction of input circuit of
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"
Microphone Preamplifier Type 2669 for ensuring compli-
ance with EMC requirements
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61
2
34
5
940904e
+ V
– V (0 V)
Chassis
Preamplifier
input:
internal view
Polarization
Voltage
100 k
+
–
Generator for
charge injection
~