Chapter 6 — Pressure-field
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" Microphone Type 4192
Effect of Temperature
Falcon™ Range of Microphone Products
Microphone Handbook
Brüel & Kjær
6
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22
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.
6.10.3 Long-term Stability
Over a period of time, the mechanical tension in the diaphragm will decrease due to
stretching within the foil. This mechanism, which, in principle, causes an increased
sensitivity, is, however, very weak for the microphone. Measurement of this mecha-
nism is not possible at room temperature.
At present, no exact value can be given for the microphone’s long-term stability but
measured changes at high temperatures indicate that Pressure-field
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" Micro-
phone Type 4192 is more than 10 times more stable than traditional Brüel&Kjær
microphones. This indicates typical changes of less than 1dB in 5000 years.
6.11 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 300°C.
When the microphone is subjected to temperatures above 200°C, it may be discol-
oured but its functionality will remain unaffected. See section 6.10.2 for permanent
changes in sensitivity at temperatures above 170°C.
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