Chapter 3 — Prepolarized Free-field
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" Microphone Type 4189
Effect of Temperature
Falcon™ Range of Microphone Products
Microphone Handbook
Brüel & Kjær
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changed within the next 10hours by a similar value. These changes are due to
decreasing charge of the electret.
Note:
special adaptors (inserted between the microphone and preamplifier) must be
made for high-temperature applications in order to protect the preampifier from
heat conduction and radiation.
3.10.3 Long-term Stability
The microphone’s long-term stability is determined by the stability of the electret
charge. The charge decays very slowly even in humid conditions. See Brüel&Kjær
Technical Review no. 4, 1979 and the specifications given below:
>1000 years/dB (dry air at 20°C)
>2 hours/dB (dry air at 150°C)
>40 years/dB (air at 20°C, 90%RH)
>1 year/dB (air at 50°C, 90%RH)
3.11 Effect of Temperature
By careful selection of materials, optimization of the design and artificial ageing,
the effect of temperature has been made to be very low.
The microphone has been designed to operate at temperatures from –30 to 150°C.
See section 3.10.2 for permanent changes in sensitivity at temperatures at 150°C.
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