6.2.5. Microphone Extension Cables
These
cables
(Fig.6.17) should
be
fitted
between the input
stage
and
the
Meter. Due
to
the limited current handling capacity
of
the
input
stage,
extension cables
are
liable
to
produce
distortion
of
the signal. A knowledge
of
the maximum voltage and maximum frequency
of
a signal
is
an
aid
to
choosing the maximum permissible length
of
extension cable before distor-
tion
is
introduced. The maximum permissible length
of
extension cable
can
be
determined
from
F ig.6. 18.
An
example
of
its
use
follows:
If
a signal
has
a maximum voltage
of
3.16 V (sin) and a maximum fre-
quency
of
11
kHz then
an
extension cable
of
type
AC
3028 should
not
exceed
20m
in length
and
a cable
of
type
AC
3029,
12m.
Suitable cables
from
the 8 & K standard cables shown in Fig.6.17
can
therefore
be
selected.
AO 0027
JJ
0110
AC
3028 JP 0023 AO 0028
CEIJD=1J=C111=D
10m
AO 0029
Fig.6.
17.
Microphone extension cables
6.2.6. Microphones
The
8 & K Condenser Microphones which
are
suitable
for
use
with
the
2209
are
shown in Fig.6.19. The microphones
are
designed
for
linearity
of
response
over the widest possible frequency
range
and feature good
temperature stability and
excellent long term stability.
Each
microphone
size
except the
1/8
inch
is
available
with
frequency
response
linear
for
0°
incidence free field measurements or
for
linear pressure response over the
widest possible
range
of
frequencies. The
1/8
inch microphone
has
little
81
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