BRUEL & KJAER 4111 - Connecting the Microphone 4111

9
phone Amplifier 2601 or Analyzer 2105 or 2109, a reference voltage
can be put on the input of one of the last instruments. The cathode
follower' s output is then compared with this reference voltage and
gives at once the applied sound pressure with the aid of the micro-
phone sensitivity as defined.
The temperature coefficient for the whole microphone 4111 is less
than o. o2 db per degree centigrade in the range -20 to +60° C, while
the change in sensitivity caused by a variation in humidity is negligible.
The response is linear up to a voltage output of 20 volts, and the dis-
tortion is less than 1 o/o for sound pressure levels up to 120 db above
-4
the reference value 2. 10 fbar, and less than 411/o for sound pressure
levels up to 140-160 db. Higher sound levels will damage the micro-
phone diaphragm.
CONNECTIONS
Microphone Amplifier 2601: The socket . for the condenser microphone
is here placed on the top of the apparatus, so that the amplifier can
act as a stand for the microphone. In order to secure a solid con-
nection between the microphone plug and socket, the plug is provided
with a union nut for screwing over the socket. An input switch selects
either this condenser microphone or the single pole input on the front
side of the apparatus.
Analyzers 2105 and 2109: The condenser microphone socket is here
placed on the front side of the instruments. In this case the input