EasyManuals Logo

BRUEL & KJAER 2221 User Manual

BRUEL & KJAER 2221
32 pages
To Next Page IconTo Next Page
To Next Page IconTo Next Page
To Previous Page IconTo Previous Page
To Previous Page IconTo Previous Page
Page #8 background imageLoading...
Page #8 background image
constant
level
which
if
maintained
for
a
period
of
1
second
would
have
the
same
A-weighted
acoustic
ener-
gy
as
the
measured
noise
event, and
is
defined
as:
1
/+oo
(p(t))2
SEL =
10
Log10 - -
dt
Tref
_oo
Po
Tref = 1 s
The SEL is
used
primarily
to
de-
scribe
and
compare
single
events
(e.g.
vehicle
pass-by,
etc.).
Max.
Hold
"Fast/Slow"
This is
the
maximum
A-weighted
RMS
sound
level
measured
with
the
standardized
"Fast"
(Type
2221)
or
"Slow"
(Type
2222)
time
constant,
over
the
measurement
period.
It
is
used
for
fluctuating
noises.
Max.
Hold
"Peak"
The
peak
value
of
impulsive
noises
is an
important
factor
when
consid-
ering
hazard
to
hearing.
The
rise
time
is 30
J.LS,
and
the
frequency
re-
sponse
linear.
Description
Principle: (see
block
diagram)
The
basic
function
of
the
instru-
ment
is
to
perform
the
Leq
measure-
ment/calculation
for
any
period
up
to
2,
77
hours.
The
Leq
measurement
principle
is
described
in
greater
de-
tail
below
since
the
SEL and
Max.
Hold
functions
are
obtained
on
the
basis
of
Leq
measurement.
The
amplified
and
A-weighted
sig-
nal
from
the
microphone
is
squared
through
the
log
and
antilog
convert-
ers. The
integrator
summates
the
signal,
generates
an
impulse
and is
reset
when
a
trigger
level is
exceed-
ed. The
impulse
repetition
rate
is
proportional
to
the
square
of
the
in-
stantaneous
value
of
the
input
sig-
nal, and
the
number
of
impulses
is
thus
proportional
to
the
noise
dose
received
since
the
beginning
of
the
measurement.
The
impulses
are
ac-
Cl;Jmulated
by
a
dose
counter.
A
crystal
oscillator
generates
clock
pulses
which
are
accumulated
in
the
time
counter.
From
the
two
counter
outputs
the
Leq
calculation
is
carried
out
by
the
microprocessor
and
re-
peated
every
0,5 s
updating
the
dis-
play.
Dose
and
time
counters
are
only
set
to
zero
when
the
instrument
is
reset.
2
Amplifier
.a.
.a.-
"A"
weighting
for
Leq•
SEL,
Max.
Hold
Fast/
Slow
- Linear
(flat)
weighting
for
Max.
Hold
Peak
• - " Fast"
for
Type
2221
- "
Slow"
for
Type
2222
Integrator
( DC/f converter)
Clock
genera
tor
AC
Output
T
Max. hold
Ma
x.
Hold
Antilog
converter
1
/T
p2 (t)
dt
Leq =
10
Log T -
p-
2
-
0 0
Micro
·
processor
Digital
display
*
Automatically
reset once per second
in Max.
Hold
T = 1
sec
. in
SE
Land
Max.
Hold
8113 13
Fig.1.
Simplified
block
diagram
of
the
Types
2221
and
2222
The SEL
measurement
procedure
is
identical
to
the
Leq
procedure,
ex-
cept
that
a
time
of
1 s is
used
for
the
calculation
instead
of
the
time
given
by
the
time
counter.
It is
possible
to
switch
between
Leq
and SEL
without
interrupting
the
measurement.
For
Max.
Hold
functions
the
loga-
rithm
of
the
instantaneous
signal
is
first
applied
to
the
Max.
Hold
circuit,
the
output
from
which
is
then
applied
to
the
Leq
circuits
for
normal
pro-
cessing.
The
Leq
of
a
constant
signal
is
equal
to
the
instantaneous
value
of
the
signal
itself.
Therefore
the
val-
ue
obtained
after
an
Leq
calculation
has
been
made
on
the
Max.
Hold
output,
is
equal
to
the
maximum
val-
ue.
For
Max.
Hold
"Fast/Slow"
the
output
is
equal
to
the
maximum
A-
weighted
signal
measured
with
the
standardized
"Fast/Slow"
time
con-
stant; and
for
Max.
Hold
"Peak"
the
output
is
equal
to
the
maximum
in-
stantaneous
value
of
the
signal
after
"Linear"
(20 Hz - 20 kHz)
filtering.
Microphone
Types
2221
and 2222
are
equipped
with
a
Prepolarized
Condenser
Mi-
crophone
Type
4176.
This
micro-
phone
is
designed
to
have
a
linear
oo
incidence
free
field
response
for
measurements
in
accordance
with
IEC
standards,
and is well
suited
for
free
field
conditions,
e.g.
most
out-
door
situations.
When
fitted
with
the
Random
Incidence
Adaptor
supplied
a
linear
random
incidence
response
according
to
ANSI
standards
is
ob-
tained,
which
generally
gives
more
accurate
results
for
indoor
measure-
ments.
The
frequency
responses
and
directional
characteristics
of
the
complete
instrument
are
given
in
Figs
3
to
5.
An
individual
calibration
chart
for
the
microphone
is
supplied
with
the
instrument.
Input
Stage
The
removable
input
stage
has
a
very
high
input
impedance
to
match
the
high
impedance
of
the
micro-
phone.
The
output
impedance
is
low
to
allow
extension
cables
to
be
in-
serted
between
input
stage
and
sound
level
meter.
Weighting
Network,
Attenuator
and
Overload
Indicator
The
selection
of
A
or
Linear
(flat)
weighting
is
automatically
made
by
the
"Function"
switch.
The
A-weight-
ing
is
applied
to
the
signal
for
Leq•
SEL and
Max.
Hold
"Fast/Slow"
measurements;
linear
weighting
is
only
obtained
for
Max.
Hold
"Peak"
measurements.
These
weightings
are
also
applied
to
the
AC
output.
A-weighted
"Peak"
measurements
may
be
obtained
by
modifying
the
instrument.
The
actual
weighting
ap-
plied
is
indicated
on
the
display.
The
input
amplifier
covers
the
range
25
to
145
dB
in
four
overlap-
ping
sub-ranges.
An
overload
indi-
cator
monitors
input
and
output
sig-

Table of Contents

Questions and Answers:

Question and Answer IconNeed help?

Do you have a question about the BRUEL & KJAER 2221 and is the answer not in the manual?

BRUEL & KJAER 2221 Specifications

General IconGeneral
BrandBRUEL & KJAER
Model2221
CategoryMeasuring Instruments
LanguageEnglish

Related product manuals