BRUEL & KJAER 2305 User guide
Level Recorder
Type
2305
AC
and
DC
level
Recording.
logarithmic
and
linear
Recording.
.polar and Rectilinear Recording,
RMS,
Average
and
Peak Recording.
50
and
100 mm
Width
of
Recording Paper.
Ink
and
Sapphire
Registering.
High Writing
Speed
and
Paper
Speed.
Synchronous Drive
with
Scanning
of
B & K Oscillators, Spectrometers, Analyzers and
Filter Sets.
BAUEL&
K~AC.R
N~RUM
,
DENMARK. Teleph
.:
800500
.
Cable
: 8RUKJA. Telex: 5316. COPEN':tAGEN
B B
230
5 -
0300036
Level Recorder
Type 2305 .
Reprint
december
1967
Contents
Page
Description
4
Controls,
Terminals
and
Mechanical Drives .
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21
Operation
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30
Accessories.
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42
Combined
Units
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Applications.
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69
Appendix
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118
Specification . . . .
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125
Description
General
Ii
Electronic
System
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6
Input
Circuit
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Range
Potentiometer
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Chopper
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6
A. C.
Input
Amplifier
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Rectifier
Response
Circuit
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7
Lower
Limiting
Frequency
Circuit
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First
Limiter
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8
Potentiometer
Range
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8
Second
Limiter
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Output
Amplifier
Section
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10
Writing
Speed
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Mechanical
System
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Principle
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Gear-Box
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Paper
Speed
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14
Sy
nchronization
Gear
1:
10 . . . .
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14
Drive
Shaft
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lIi
Friction
Clutch
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15
Single
Chart
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15
Drive
Shaft
II
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15
Two
-
Channel
Selector
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Electromechanical
System
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16
Synchronous
Motor
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Electromagnetic
Clutch
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16
Lifting
Magnet
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Event-Marker
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Writing
System
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Magnet
System
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Mechanical
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18
Paper
Holder
System
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18
Power
Supply
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19
Rectifiers
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•
19
100
mV
Ref.
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19
Mains
Frequencies
and
Voltages
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Fuses
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20
Description
General.
The
Level
Recorder
Type
2305
has
been designed
for
accura
te
recording
of
signal levels
in
the
fr
eq
u
ency
range
2 Hz
(c
I
s)
to 200000 Hz
(c
I
s)
.
Typical
fields
of
application
are
the
recording
of
frequ
e
ncy
r
esponse
characteristics,
reverberation
decay
curves,
noise
and
vibration
levels,
spectrograms,
and
polar
diagrams
.
Potenti
ometer
db-Ranll'
Fig. 1.1.
Block
diagram
of
the
Level Recorder.
f59J98
Record'
ings
can
be
made
by
means
of
ink
,
either
on
lined
paper
or
on
frequency
calibrated
paper,
or
by
means
of
a
sapphire
stylus
on
wax-coated
paper.
Different
types
of
ink
and
preprinted
recording
paper
are
available
.
A
synchronous
motor
is
used
for
the
paper
drive,
and
by
means
of
a gear-
box 12
different
paper
speeds
are
available.
The
operation
of
the
Recorder
is
based
upon
the
servo
principle
.
When
the
magnitude
of
the
voltage
applied
to
the
input
terminals
is
changed,
a
current
will flow
through
the
driving
coil
of
the
writing
system,
thus
moving
the
stylus,
which
is
mechanically
coupled
to
the
Range
Potentiometer.
By
the
movement
of
the
stylus
the
voltage
delivered
from
the
Potentiometer
to
the
input
amplifier
will be
altered
until
a
stable
condition
is
regained.
In
this
way
it
is
possible
to
obtain
recordings
for
different
ranges
of
voltage
variations
by
employing
different
Range
Potentiometers
.
Ii
Electronic System.
Electronically
the
Recorder
Type
2305
mainly
consists
of
an
input
circuit,
a
Range
Potentiometer,
a
direct-coupled
AC
input
amplifier,
the
specia
l
B & K
signal
rectifier
arrangement,
and
an
unconventional
DC
output
ampli-
fier
section
which
drives
the
electrodynamic
writing
system
(see
block
dia-
gram
Fig.
1.1).
tnput Circuit.
The
input
of
the
Level
Recorder
is
unsymmetrical.
If
desired
it
can
be
made
symmetrical
by
a
special
Input
Transformer,
see
chnpter
Accessories.
The
signal
is
first
fed
to
the
continuously
variable
input
potentio-
meter
and
then
to
the
calibrated
input
attenuator.
Great
care
has
been
taken
in
the
design
of
the
input
circuit
to
obtain
an
approximately
constant
input
impedance
of
the
Recorder.
The
impedance
varies
between
16
and
18
IdJ,
depending
upon
the
position
of
the
INPUT
POTENTIOMETER,
and
reaches
its
minimum
value
in
the
middle
and
end
positions
of
its
12
dB
range.
Due
to
stray
capacitance
in
the
input
potentiometer
the
frequency
response
will
be
influenced
to
a
small
degree
at
the
highest
frequencies.
Vide
Fig.
1.2
where
the
highest
deviations
for
the
different
positions
of
the
potentiometer
are
illustrated.
The
calibrated
INPUT
ATTENUATOR
attenuates
the
input
signal
in
six
steps
of
10
dB
with
an
accuracy
of
approximately
± 0.2 dB.
Range Potentiometer.
From
the
input
attenuator
the
signal
is
fed
to
the
Range
Potentiometer.
Different
interchangeable
Range
Potentiometers
are
available,
logarithmic
(dB
potentiometers)
as
well
as
linear,
see
also
page
45.
Each
potentiometer
consists
of
precision
resistors
connected
between
216
silver
lamellae
on
which
the
slider
of
the
driving
arm
moves,
again
refer
to
the
block
diagram
Fig.
1.1.
Chopper.
The
voltage
developed
be
twe
en
the
slider
and
ground
is
fed
to
an
electromechanical
chopper.
When
it
is
desired
to
record
AC
signals,
the
c
hopper
arm
is
continuously
in
one
of
its
two
contact
positions.
However,
if
the
Level
Recorder
is
switched
to
re
co
rd
DC
levels
,
the
c
hopper
will
operate
at
twic
e
the
mains
frequen
cy, g
iving
an
AC
input
to
the
following
amplifier.
AC
Input Amplifier.
Th
e
non-chopped
or
chopped
s
ignal
is
applied
to
the
balanced
direct-coupled
AC
amplifier
which
,
in
s
tead
of
a
conventional
AC
amplifier
has
two
distinct
advantages;
unw
a
nted
blocking
of
the
amplifier
due
to
overdriving
(and
thus
overshoot
in
the
recording)
is
eli-
minated,
and
the
innuence
of
variations
in
the
supply
vollage
is
decreased
to
a
minimum.
There
are
several
other
reasons
why
this
type
of
circuitry
is
used.
Firstly,
the
halancing
enables
the
output
from
the
signal
rectifier,
which
follows
immediately
after
the
amplifier,
to
be
symmetrical
wilh
respect
to
ground.
Secondly,
by
using
AC
as
well
as
DC
negative
feed-
6
back
the
lower
limiting
frequency
of
the
amplifier
is
very
easy
to
change.
Becaus
e
of
the
feedback
arrangements
the
DC
amplification
of
the
ampli-
fier is
approximately
270,
while
the
AC
amplification
is
in
the
region
of
4500.
Rectifier
Response
Circuit.
The
rectification
circuit
is
the
specially
designed
Briiel
& Kj!er
type,
which
can
be
switched
to
me
as
ure
the
true
RMS,
the
arithmetical
average
and
half
the
peak-to-peak
value
of
the
input
signal·).
A
bridge-type
full-wave
rectifier
for
detection
of
the
signal
allows
both
the
positive
and
negative
parts
of
the
input
signal
to
be
treated
in
the
Recorder
.
The
three
different
rectifier
characteristics
can
be
selected
by
the
switch
marked
"Rectifier
Response".
The
last
position
of
Ihis
switch
is
marked
DC,
when
in
this
position,
peak
detection
of
the
chopped
DC
Recorder
input
signal
takes
place
.
The
Rectifier
Response
networks
are
symmetrically
arranged
with
respect
to
ground,
whereby
the
output
signal
contains
no
superimposed
fundamental
AC
component
.
This
type
of
circuitry
is also
advantageous
because
of
its
insensitivity
to
mains
voltage
fluctuations.
The
amplifiers
and
Ihe
Rectifier
Response
networks
have
been
designed
10
measure
the
true
RMS
value
of
signals
with
crest
factors
up
to
5 (crest
factor
=
peak
voltage
/ RMS voltage).
Correct
measurements
of
arithmetical
average
values
are
possible
for
signals
with
the
product:
form
factor
X
crest
factor
= 5, i.e.
peak
voltage
/
average
voltage
= 5.
The
peak
rectifier
measures
half
peak-to-peak
value
which
should
Le
horne
in
mind
when
unsymmetrical
signals
are
being
measured.
Further,
as
a
certain
amount
of
energy
is
dissipated
within
the
rectifier
circuit,
the
true
peak
value
of
very
narrow
pulses
cannot
be
correctly
measured
. It
has
therefore
been
found
convenient
to
calibrate
the
peak
rectifier
to
accurately
measure
sinusoidal
signals,
whereby
the
peak
values
measured
on
square-wave
signals
(crest
factor
=
1)
and
very
narrow
pulses
will
in
the
first
instance
be
slightly
too
high
a
nd
in
the
second
too
low
.
Refer
also
to
Appendix.
When
non-sinusoidal
signals
containing
important
frequency
components
in
the
neighbourhood
of
the
lower
or
upper
limiting
frequency
of
the
recorder
are
being
measured,
the
recorded
peak
level
will
be
incorrect,
due
to
phase
distortion
in
the
amplifiers
.
The
recorded
average
level
will
only
be
in-
fluenced
to
a
very
small
degree
by
the
phase
shift,
whereas
the
RMS
recording
is
Independent
of
any
phase
distortion.
Curves
concerning
this
are
found
in
the
Appendix.
Lower
Limiting
Frequency
Circuit.
Following
the
Rectifier
Response
circuit
is
the
Lower
Limiting
Frequency
circuit,
which
allows
for
a
first
averaging
of
the
level
of
the
measured
signal.
(Refer
part
Appendix
in
this
book).
*)
A
th
o
rou
gh
description
of
the
functi
oni
ng
of
thi
s
circuit
is given in
the
B & K Tec
hnic
al
Review
No.
3-
1958,
4-1960
a
nd
1-1
96
1.
7
This
circuit
determines
the
lowest
frequency
to
which
the
Recorder
responds
correctly.
It
can
be
set
to
five
values
2, 10, 20, 50
and
200
Hz
(cis)
by
the
knob
LOWER
LIMITING
FREQUENCY
.
In
Fig.
1.2
can
be
seen
the
response
at
the
five
different
settings
.
It
should
be
noted
that
at
the
various
frequency
limits
marked
around
the
knob
the
reading
is
decreased
by
approximately
0.3 dB
only
. As
the
stability
of
the
complete
writing
system
is
dependent
on
the
combined
setting
of
the
LOWER
LIMITING FREQUENCY,
WRITING
SPEED
and
POTENTIOMETER
RANGE
the
reader
is
referred
to
the
com-
me
nts
under
"Writing
Speed",
pag
e
10
.
~~
SOCIS
ODets
5dB
10
100
1000 10000
Highest
dev
i
otl
'
OO
a
n
~=
to be found f:lr
E~
any
setting
of
====
" Input Potentiometer"
5
100
000 2 CIS
16(807
Fig. 1.2.
Typical
frequency characteristics
of
the
Level
Recorder
for
different
settings
of
LOWER
LIMITING FREQUENCY switch.
The
two
dotted
lines at
the
high
frequencies give
the
greatest deviation to be
found
for
any
setting Of
INPUT
POTENTIOMETER.
First
Limiter.
To
avoid
overdriving
(heavy
charging
of
the
condensers
in
the
Lower
Limiting
Frequency
circuit)
by
high
and
very
rapid
fluctuations
in
the
input
signal
level,
an
amplitude
limiter
is
introduced.
The
threshold
of
the
limiter
is
designed
so
that
the
drive
system
has
full
power
when
the
signal
fluctuations
reach
its
limit.
Potentiometer
Range.
The
output
signal
from
the
first
limiter
network,
which
is
now
DC, is
compared
with
a
built-in
balanced
DC
reference
voltage,
the
signal
difference
then
being
used
to
drive
the
output
amplifier
via a
second
limiter.
The
difference
signal
obtained
by
comparing
the
rectified
and
limited
input
signal
with
the
buill-in
reference
voltage
is
attenuated
in
a
step
attenuator
marked
POTENTIOMETER
RANGE.
By
the
different
positions
of
the
atte-
nuator
the
resolution
of
the
Recorder
is
determined.
(See
also
"Controls,
Terminals,
and
Mechanical
Drives",
page
22) .
The
resolution
of
the
Recorder
means
the
degree
by
which
the
Recorder
is
able
to
record
the
details
in
signal
level
variations.
Fig
. 1.3
illustrates
the
effect
of
the
resolving
power
for
different
settings
of
POTENTIOMETER
RANGE.
The
four
measurements
8
were
made
by
means
of
a
step
voltage
on
the
input
of
the
Recorder
and
with
a 50 dB
Range
Potentiometer
inserted.
It
is
seen
from
the
figure
th
at
with
a
POTENTIOMETER
RANGE
setting
of
"10"
the
resolving
power
is too
high
for
the
Range
Potentiometer
used,
thus
the
writing
system
tends
to
over
·
shoot.
By
choosing
position
"50"
it
is
seen
that
the
"corners"
of
the
step
voltage
are
sharp,
i.e.
the
correct
position.
In
position
"
80"
the
resolving
power
is too low,
the
"corners
"
are
thus
rounded
off
.
.
OO
OOOOOOOOOOOOOOOOOOOGOOOOOOOOOOOOOOOOOOOOOOOOOOO
_
...
_
...
_
...
·~O
·
db
'20
"
db
'SO "
db
"eO
"
db
Paper
Speed
10
mm/nc
. _
Fig. 1.9.
Effect
of
resolving
power
(POTENTIOMETER
RANGE
setting). A
50
dB
Range Potentiometer was used,
WRITING
SPE
ED on "500",
LOWER
LIMITING FREQUENCY -60
Hz
(cIs"
and
measuring
frequency
600 Hz (cIs).
I
When
employing
logarithmic
Range
Potentiometers
the
signal
voltage
differ·
ence
between
any
of
the
lamellae
is
equal
in
percent,
i.e.
the
optimum
resolv·
ing
power
setting
will
be
the
same
for
any
deflection
of
the
stylus.
With
linear
Range
Potentiometers,
however,
the
signal
voltage
difference
in
percent
between
the
lamellae
at
one
end
of
the
lamellae
face is
not
the
same
as
the
difference
at
the
other
end,
which
means
that
the
optimum
resolving
power
will
not
be
identical. A
10-35
mY
linear
Range
Potentiometer
requires
for
about
full deflection
of
the
stylus
an
optimum
resolving
power
setting
of
"10"
and
for
about
zero
deflection
a
setting
of
"25",
whereas
a
10-110
mY
Potentiometer
requires
a
setting
of
"10"
and
"80"
respectively.
In
practice,
the
resolving
power
(POTENTIOMETER
RANGE setting) is
mostly
chosen
to
a
value
between
the
two
limits
covering
most
deflectio
ns
of
the
stylus,
refer
to
part
"
Control,
Terminals
and
Mechanical
Driv
es",
page
22.
Second
Limiter,
From
the
Potentiom
e
ter
Range
altenuator
the
signal
is
fed
to
the
second
amplitude
limiter.
The
limiter
ensures
that
the
drive
signal
to
the
output
amplifier
section
is
independent
of
the
magnitude
of
the
servo
9
error
signal
as
soon
as
this
reaches
a
certain
value.
That
means
that
the
signal
to
the
output
amplifier
section
will
have
a
constant
value.
Output Amplifier
Seetion.
This
section
consists
of
a
chopper
amplifier
and
a
push
-
pull
type
DC
power
amplifier.
The
chopper
amplifier
is
introduced
to
prevent
zero
level
drift
during
the
amplification
of
very
small
DC
signals.
Its
chopper
frequency
is 5
kHz
(kc/s). A
balanced
modulator
is used
as
chopper,
the
working
principle
of
which
is
illustrated
in
Fig. 1.4.
When
the
chopper
signal
has
been
amplified
in
two
stages
it
is
rectified
in
a
phase-
sensitive
rectifier
circuit
(i.e.
balanced
demodulator)
and
then
used
to
control
the
DC
power
stage.
This
latter
stage
operates
as
a
type
of
single-
ended
push-pull
amplifier,
thus
allowing
one
terminal
of
the
drive
coil in
the
electromagnetic
recording
system
to
be
grounded.
+DC--'---~==r------7~------~~--'
Voltage
v_
O
'
+---~--
__
-
time
Chopper
Oscillator
~--,-
__
AC
Voltage
time
fiO¥I,.8
Fig. 1.4.
Sketch
illustrating the operation
of
the
electronic
chopper
in the
DC
output
amplifier.
Writing
Speed.
From
a
special
winding
on
the
moving
coil
in
the
electro·
dynamic
drive
system
a
velocity
dependent
signal
is
developed
.
This
signal
is
introduced
as
negative
feedback
to
the
input
of
the
output
amplifier
section
.
The
feedback
signal
will
completely
control
the
output
signa
l
from
this
section
as
long
as
the
signal
derived
from
the
second
amplitude
limiter
has
a
constant
value,
which
is
the
case
when
the
limiter
is
in
opera
[ion.
In
this
way
a
constant
speed
of
the
writing
system
is
obtained.
The
speed
and
thereby
the
damping
(averaging
time)
of
the
writing
system
can
be
adjusted
by
means
of
the
attenuator
marked
WRITING
SPEED.
Refer
to
the
curves
Fig. 1.5
and
also
to
part
Appendix
in
this
book
.
As
mentioned
under
"Lower
Limiting
Frequency"
the
stability
of
the
com·
plete
writing
system
is
dependent
on
the
combined
settings
of
the
WRITING
10
SPEED,
LOWER
LIMITING FREQUENCY
and
POTENTIOMETER
RANGE.
When
the
two
first
knobs
are
combined
so
that
their
settings
correspond
to
points
inside
the
hatched
area
in
Fig
. 2.2
on
page
24,
the
writing
system
will
always
be
in
a
stable
condition,
presuming
that
the
POTENTIOMETER
RANGE
knob
is set
according
to
the
Range
Pot
e
ntiometer
used
.
For
instance
at
"50"
for
a 50 dB
Rang
e
Potentiometer.
Wh
en
settings
are
chosen
outside
the
hatched
area,
the
writing
system
lends
to
overshoot
and
to
be
unstable
.
.
0000000000
0000000000000
00
0000000000000
0000000000
0
W.
S'
IW
.'
Paper
Spied
.100
mm/
••
c.
-_
W.S.·
Writing
Sp.ed
In
mm/.lc.
Fig. 1.5. Curves
showing
the
influence
of
the
writing speed
upon
the
recording
of
an
input
step
voltage
on
100
mm
paper.
Mechanical System.
The
Level
Recorder
Type
2305 is
designed
to
fulfil
a
number
of
operational
requirements
in
combination
with
other
Briiel & Kjrer
instruments
and
yet
at
the
same
time
be
remotely
controlled
.
To
carry
this
out,
various
mechanica
'l
gears,
clutches
and
electromechanical
switches
are
necessary
,
Principle.
In
Fig. 1.6
the
mechanical
drive
system
is
illustrated,
and
with
the
aid
of
this
figure
the
working
principle
will
be
explained.
The
motive
power
is
supplied
from
the
self-starting
synchronous
motor
via
a
worm
drive
to
the
electromagnetic
clutch
.
From
the
clutch
the
power
is
transferred
to a
gear-box
via
the
two
nylon
gear
wheels 1
and
2.
The
gear-
box (described below)
has
two
output
shafts,
Drive
Shaft
1
and
Drive
Shaft
II,
the
speeds
of
which
can
be
chosen
by
the
PAPER
SPEED
and
DRIVE
SHAFT
SPEED
knobs
respectively
.
Drive
Shaft
1.
This
has
a fixed
gear
wheel
3
which
among
others
drives the
reduction
gear
sets
4, 5
and
6,
7.
The
set
6, 7 is
free-running
on
the
Drive
11
Shaft
I.
Two
speeds
(1
: 10)
can
be
transferred
to
the
gear
wheel
9
by
placing
the
gear
wheel
8
in
the
position
shown,
or
in
position
"in",
where
it
will,
in the
latter
case,
be
mechanically
connected
with
the
wheel
6.
The
wheel
8
is
shifted
by
the
Synchronizing
Gear
Lever
X (Fig. 1.8
and
2.3).
When
the
Synchronizing
Gear
Lever
is
shifted
to
its
"in"
position
(Lever X
pulled
out) a
cam
disc
functions
against
a
microswitcb
which
controls
the
Single
Chart
automatic
stop.
The
gear
wheel
9 is
mechanically
connected
with
the
paper
drive
spindle
via a
friction
clutch.
Synchro-
nous
Motor
Electromognetic
Clutch
2112
Driv~aft
Speed
Gear
Box
/ 5
~
Chain Wheel
t------t-:.Po:-:!!":!.::~:.E~:~:-::t~I'tHt_-
Drive
Shaft
I
Paper
Drive
Sprocket
Cam Disc
~~~~
Grooved
Finger
/ Wheel
,t
Friction
Clutch
xl
Shown
with
Gear Lever pushed
in
,
i.e
.1:
10
gear
not
operating
161808
Fig. 1.6. Illustration
of
mechanical
sy
stem
out
side tile gear-box.
On Drive
Shaft
I a
cam
disc is also
mounted,
which
provides
mechanically
the pulses IIsed
to
control
the
filter
switching
in
the
B & K Audio
Frequency
Spectrometer
Type
2112
and
Band-Pass
Filter
Set
Type
1612
when
these
are
used
in
conjunction
with
the
Recorder.
Drive
Shaft
II.
This
can
be
given
any
speed
of
revolution
in
relation
to
the
paper
drive
sprocket
by
operating
the
knob
DRIVE
SHAFT
SPEED.
On
the Drive
Shaft
II
is
mounted
a
cam
disc
which
operates
a
microswitch
for
the
Two·Channel
Selector.
Gear-Box. A
number
of
toothed
wheels
mounted
together
in
pairs
and
placed
on
two
spindles
enable
gear
ratios
of
1 : 3.333, 1 : 3, 1 : 3.333, 1 : 3,
etc
.
to be developed successively
along
the
greater
wheels
on
spindle
A (vide
Fig. 1.7)
on
which
is
also
mounted
the
nylon
gear
wheel
2.
A
moveable
wheel, B, is used
to
transfer
the
rotation
of
any
selected wheel
on A
to
the
elongated
gear
wheel,
C,
which
drives
Drive
Shaft
I. A
duplication
of the
wheels
Band
C serves
to
drive
the
Drive
Shaft
II
.
The
two
moveable
12
wheels B
are
each
shifted
to
the
various
positions
by
means
of
a
toothed
sector
operated
by
toothed
wheels
of
which
one
is
shown
to
the
right
in
Fig
. 1.7.
The
latter
are
directly
connected
with
the
two
knobs
on
the
top
panel
which
are
marked
PAPER
SPEED
and
DRIVE
SHAFT
SPEED
respectively
.
Any
change
of
gear
can
be
carried
out
while
the
gear·box
is
operating
.
Fig. 1.7. Gear-box and shifting arrangement for Paper Speed and Drive Shaft
Speed.
To give
an
illustration
of
where
and
how
the
most
important
electro·
mechanical
and
mechanical
parts
of
the
Recorder
are
located
,
the
reader
is
referred
to
the
"exploded" view
in
Fig
. 1.8.
Paper
Speed.
The
paper
speed
can
be
freely
chosen
among
10
plus
two
additional
values,
where
the
highest
will be 100
mm/sec
and
the
lowest
0.0003
mmlsec.
The
accuracy
of
the
speed
is solely
determin
ed
by
the
fre·
quency
of
the
power
supply
as
the
motive
power
is
derived
from
a
syn·
13
chronous
motor.
Around
the
knob
PAPER
SPEED
are
printed
two
scales
of
figures,
the
large
figures
correspond
to
the
paper
speeds
obtained
when
the
Synchronization
Gear
1 : 10 is
not
engaged,
this
means
the
Lever
X is
pushed
in,
whereas
the
small
figures
give
the
paper
speeds
for
the
opposite
position
of
Lever
X.
The
relationship
between
the
speed
of
rotation
of
the
Drive
Shaft
I
and
the
paper
speed
can
be
seen
in
the
table
below.
Paper
Speed
I 100 30 10 3 1 0.3 0.1 0.03 0.01 0.003
mm/sec.
10 3 0.3 0.1 0.03 0.01 0.003
0.001
0.0003
Drive
Shaft
I I
r.p
.m. 120 36 12 3.6 1.2 0.36 0.12 0.036 0.012 0.0036
Synchronization
Gear
1:
10.
This
"extra"
gear
has
been
included
in
the
Recorder
to
obtain
synchronous
drive
of
a Briiel & Kjrer
Oscillator
or
Analyzer
scanning
mechanism
with
the
corresponding
frequency
calibrated
recording
paper.
The
Gear
Lever
X,
see Fig. 2.3
on
page
26, is accessible
on
the
right-hand
side
cover
of
the
Recorder.
When
the
Lever
is
pulled
out,
the
1:
10 Gear
is engaged. Any
change
can
be
made
while
the
mechanical
system
is in
operation
without
risk
of
damage
.
Drive
Shaft
1.
This
mechanical
drive
is
intended
to be
used
in
connection
with
recording
on
preprinted
frequency
calibrated
paper.
The
scanning
system
of
the
respective B & K
Oscillator
or
Analyzer is
mechanically
Out-in
Co
ntrol
at Pul
51
Switch
Ma
gn,
t for E
V1!nt
Marking
Co
ntrol
G
eO
f Shift
Con
trol
~Paper
Spie
d m
l1'l,l\;
lc:'
/
GearShift
Control
I
-Drive
Shaft
Spud
r.
p.m:'
Nylon
Gea
r Wheels
(to"
..
plac.
d
w~.~
<""ngl
ft,po,.."
...
ppI,
I
••
qu.",,)
.
Remote Control Jock
Two-Channel
Silector
Terminals
~
~
~-"
"
.
-
~.
,-
~®
I
Grooved Finger
Wh
..
l
Sy
nchronizing Gear Llvlr
Ou
t-
In
Control of
Two
-Channel
S,llct:'r
fO
o
H!I
Fig. 1.B.
"Explod
ed" view
of
the
Level Re
cord
er me
chanical
syst
em .
14
connected
to
Drive
Shaft
I via a
special
Flexible
Shaft
VB
0040
or
in
the
case
of
the
combined
instruments,
which
are
mounted
together
in
a steel
cabinet,
via
a
chain
drive.
When
the
B & K
Audio
Frequency
Spectrometer
Type
2112
or
the
Band·Pass
Filter
Set
Type
1612
are
employed
the
filter
switching
of
th
ese
apparatuses
is
also
con
troll
ed
from
Drive
Shaft
I
but
in
this
case
electrically
via
a
microswitch
(vide
Figs.
1.6
and
1.8).
The
switch
can
be
removed
from
touching
the
cam
disc
by
the
screwdriver·
operated
Out-In
Control
S
accessible
on
the
plate
where
the
pilot
lamp
is
situated,
see
also
Fig. 2.3.
As
both
the
speed
of
Drive
Shaft
I
and
the
paper
is
controlled
by
a
single
knob
(
PAPER
SPEED),
Ihe
speed
may
be
changed
during
the
reeording
of
frequency
response
curves
or
spectrograms
without
upsetting
the
synchronism
between
the
Oscillator/Analyzer
and
the
recording
paper.
To
avoid
damage
to
the
gear
wheels
,
the
torque
supplied
from
Drive
Shaft
I
should
not
exceed 2
kg
cm.
FrictIon
Clutch.
'Vilh
a
view
to
giving
easy
and
exact
synchronization
he
tween
the
starting
point
of
a
recording
on
the
recording
paper
and
the
sca
nning
device
of
the
connected
oscillator
or
analyzer
the
paper
rlrive
sprocket
can
be
mo
ved
with
respect
to
the
position
of
Drive
Shaft
I
by
means
of
a
grooved
finger
wheel
Z (vide
Figs
. 1.8
and
2.3) .
This
has
been
made
possible
by
the
use
of
a
friction
clutch,
see
Figs.
1.6
and
1.8.
Single
Chart.
An
important
device
which
is
controlled
via
the
paper
drive
spin(lIe is
the
automatic
stop
switch
.
This
switch
is
operated
by
a
cam
disc
on
the
1 : 10
Gear
axle
when
the
Gear
is
engaged
(Lev
er
X
pulled
out)
and
activates
the
electromagnetic
clutch
after
one
complete
rot
a
tion
of
the
axle.
Each
rotation
of
the
cam
corresponds
to
one
chart
length
of
preprinted
reco
rding
paper
(250
mm).
Thus
.
as
the
automatic
stop
switch
is
connected
in
the
start-slop
circuit
of
th
e
electromagnetic
clutch
the
recording
of
single
cha
rts
is
made
possible
.
DrIve
Shaft
II.
Since
the
speed
of
this
shaft
is
independ
e
nt
of
the
paper
speed
as
is
mentionl'd
previously,
any
frequency
response
curve
or
spectro·
gram
('an he
recorderl
in
an
en
la
rged
or
compressed
fr
e
quency
scall'.
providing
the
Oscillator
or
Analyzer
controlling
the
Recorder
input
signal
is
driven
from
Drive
Shaft
11
instead
of
from
Drive
Shaft
T.
The
DRIVE
SHAFT
SPEED
and
the
PAPER
SPEED
have
the
same
numher
of
positions,
Ihal
means
if
they
are
bolh
se
t
in
the
same
position
(examp
le
PAPER
SPEED
on
"10/1"
and
DrnVE
SHAFT
SPEED
on
"12")
the
two
Drive
Shafts
T
and
IT
will
rolale
at
Ihe
same
speed.
The
safe
torque
supplied
from
Drive
Shaft
II
is
the
same
as
specified
for
Drive
Shaft
T.
It
is also
possible
to
us
e
DRIVE
SHAFT
II
with
the
combined
units
when
the
accesso
ries
VT
0018
are
fitt
ed
to
the
Level
Recorder.
See
rlescriplion
at
the
beginning
of
chapter
5.
1Ii
Two-Channel
Selector.
This
selector
is
operated
by
means
of
interchangeable
cam discs
mounted
on
the
Drive
Shaft
II
and
can
be
used
for
a
number
of
purposes,
such
as
time
marking,
two-channel
intermittent
recordings,
control
of
external
switching
systems,
automatic
recording
of
reverberation
curves,
etc.
The
Two-Channel
Selector
can
be
moved
out
of
function
by
means
of
a
cam
arrangement
whioh
can
be
screwdriver-operated
through
the
right-hand
cover plate, see Fig. 2.3.
Electromechanical System.
The
electromechanical
circuit
consists
of
the
drive
motor,
the
electromagnetir
clutch
and
the
event-marking
and
pen-lifting
arrangements.
Synchronons
Motor.
The
motor
is
of
the
single-phase
synchronous
type.
The
rotating
electromagnetic
field is
produced
by
connecting
a
capacitor
in series
with
one
of
the
three
motor
windings
and
connecting
this
series L-C circuit
parallel
to
one
of
the
two
remaining
windings.
Dependent
upon
which
one
of
the
windings
is
paralleled
by
the
series circuit,
the
motor
will
rotate
in
one
or
the
other
direction
.
The
direction
of
rotation
is
controlled
by
means
of
the
switch
marked
FORWARD-REVERSE
on
the
Recorder
top
panel,
see
also Fig. 1.9.
o
,:
~----,
Forward
: Reverse
I
Power Supply
Event
Marking
Event
Marker
Switch for
2112
Control Pulses
/'
~DriV.
Shaft
I
Lifting
Magnet
.)To
be
used
with
Com-
bined Units
Type
3313 and
3326
Two-Chomel
Selector
160~.5f
Fig. 1.9. Basic diagram
of
the
electromechanical circuit.
Electromagnetic
Clutch.
To
allow
immediate
transfer
of
drive
power
at
correct
speed
of
rotation
when
the
recording
is
started,
the
motor
can
be
kept
running
and
the
recording
commenced
by
connecting
the
motor
to
the
gear-box
with
the
aid
of
an
electromagnetic
non-slip
clutch. A switch
marked
16
START-STOP
on
the
Recorder
controls
the
current
in
the
electromagnet.
When
current
flows
in
the
coil
of
the
magnetic
clutch,
the
motor
is discon-
nected
from
the
gear-box,
while
with
no
current
flowing
the
motor
is
mechan-
ically
switched
in.
This
method
of
operating
the
clutch
has
been
chosen
to
avoid
the
complexity
of
a
rotating
electromagnet
and
slip-ring
arrangement.
Lifting
Magnet.
As
the
motor
can
be
reversed,
it
is
easy
to
record
a
number
of
curves
on
the
same
sheet
of
recording
paper
without
losing
the
syn-
chronization
between
the
Recorder
and
any
externally
connected
instrument
,
such
as
an
Oscillator
or
Analyzer.
However,
to
avoid
the
recording
of
a
possible
curve
when
the
motor
is
reversed,
an
electromagnetic
pen-lifting
arrangement
automatically
lifts
the
two
pens,
the
writing
stylus
and
event-
marker
from
the
paper
when
the
motor
is
switched
to
"Reverse".
The
Lifting
Magnet
can
also
be
controlled
externally
via
the
7-poled REMOTE
CONTROL
jack
(see Fig. 1.9),
the
voltage
supply
for
the
magnet
then
being
taken
from
the
Recorder
via
the
same
jack.
Event-Marker.
In
many
cases
it
may
be
convenient
to
mark
a
certain
event
on
the
recording
paper
during
operation.
For
this
purpose
a
separate
marker
pen
has
been
provided,
which
marks
the
outer
rim
of
the
paper
between
the
edge
and
the
perforated
holes
that
slot
into
the
paper
drive
sprocket.
The
movement
of
the
marker
pen
is
operated
by
means
of
an
electromagnet.
The
marking
is
controlled
from
the
EVENT-MARKNG
pushbutton
on
the
Recorder
top
panel,
but
can
also
be
remotely
controlled
via
the
REMOTE
CONTROL
jack,
Fig. 1.9.
Writing
System.
Magnet
System.
The
electrodynamic
writing
system
constitutes
a
most
im·
portant
part
of
the
Level
Recorder.
It
has
been
designed
as
a closed
magnetic
circuit
producing
a
homogeneous
field,
within
which
the
driving
and
the
feedback
coils move, vide Fig. 1.10. A
max.
force
of
approximately
1
kg
is
developed
during
operation.
The
coils
are
guided
within
the
magnetic
system
by
means
of
two
metal
rods
and
electrically
connected
via
four
brushes
and
slip-ring
strips
.
..
...
~
....
~~)6
Fig.
1.10.
The
electrodynamic
writing
sy.tem
.
fore_ld
l
...
'
....
pot.rot_t.t
17
The coil
assembly
is
mounted
in
the
magnet
system
by
means
of
the
three
screws
marked
S
in
Fig. 1.10.
If,
for
any
reason,
it
should
be
desired
to
remove
the
coil
assembly
from
the
magnet,
this
can
be
readily
done
by
unscrewing
the
screws
S
and
pulling
the
'coil
assembly
out,
together
with
the
center
pole
piece.
NOTE:
During
dismantling
the
coil
assembly
care
should
be
taken
that
the
magnetic
field
in
which
the
coil
normally
moves, is
not
at
any
instant
opened.
This
can
be
obtained
by
either
substituting
the
coil
assembly
with
an
iron
rod
with
the
same
dimensions
as
the
center
pole piece
or
by
mounting
an
external
iron
tube
around
the
magnet.
Mechanical.
The
driving
arm
of
the
moving
coil
assembly
is
connected
to
the
mechanical
writing
system
by
means
of
a
wishbone
spring
head,
the
system
being
so
designed
to
give a
free
choice
of
100
mm
or
50
mm
writing
width.
By
fixing
the
wishbone
in
one
of
the
two
different
holes
in
the
mechanical
writing
system,
the
drive
arm
will
propel
the
bogie
with
the
penholder
to
traverse
100
mm
or
50
mm
paper
respectively.
The
penholder
can
hold
both
sapphires
and
inking
pens
.
The
pressure
of
the
mounted
sapphire
or
pen
on
the
recording
paper
can
be
adjusted
by
a
screw J (Fig.
3.1
page
31).lt
is
pre·adjusted
at
the
factory
and
will
normally
amount
to
around
15
grammes.
*)
Paper
Holder
System.
(ReIer Fig. 3.1 on page 31).
To allow
accurate
alignment
of
the
zero line
on
the
paper
with
the
zero
mark
on
the
mechanical
writing
system
scale,
the
scale
which
is
spring.
loaded is
adjustable
by
a
tension
screw
on
the
right-hand
side
of
the
writing
arm
unit. A
cam
screw
K
located
on
the
scale
varies
the
pressure
of
the
paper
guide clip E,
thereby
allowing a
variety
of
paper
thicknesses to
be
used. More
details
about
the
various
methods
of
alignment
can
be
found
under
Operation.
A
demountable
stainless
steel
cutting
blade
supplied
with
the
Recorder
is
inserted
at
the
front
plate
beneath
the
writing
plate
in
order
to give clean
detachment
of
recorded
paper
from
the
roller.
It
is
so
spaced
that
provided
one
of
the
frequency
calibrated
papers
QP
0123,
QP
0223, QP 0323
or
QP 1123 is used,
and
the
Recorder
is
stopped
prior
to
detachment
in
a
position
so
that
the
writing
system
stylus
rests
around
the
10
Hz (cis)
line
on
the
next
chart,
the
recording
will
always
be
detached
including
the
formal
which
allows
object
measured,
paper
speed
etc.
to
be
noted
.
*)
For
the
paper
types QP
0402
and
QP
0423
the
pressure
should be readiusted to around
20
grammes.
IH
Power
Supply.
Rectifiers.
The
power
supply
section
of
th
e
apparatus
contains
two
full·
wave
and
two
half·wa
ve rectifiers.
One
of
the
full·wave
rectifiers supplies
the DC
for
the
magnetic
clutch,
the
event
marking
arra
ngement,
and
the
lifting
magnet.
The
AC
ripple
of
thi
s
rectifier
is
us
ed to
dri
ve
th
e electro·
mec
hanical
chopper
in
th
e
Recorder
input
circuit.
The
output
voltage is
24
volts
and
is
also
available
at
th
e
7'pin
socket
for
re
mote
co
ntrol,
see
Figs. 1.9
and
2.3.
Ex
te
rn
al loads
placed
across
the
24
volts DC
should
not
draw
more
than
250
rnA')
of
curr
ent.
The
second
full·wave
re
ctifier
supplies
the
plate
voltage
to
all the amplifier
tubes
with
the
exception
of
the
tubes
in
the
DC
output
stage.
The
positive
reference
voltage
for
the
servo
system
is also
supplied
from
this
rectifier
and
stabilized
by
means
of
a
Zener
diode
.
Both
half·wave
rectifiers
are
supplied
from
the
same
section
of
the
trans
·
former
winding
and
act
as
a
type
of
voltage
doubling
circuit. One
of
the
half
·wave
rectifiers
supplies
the
positive
and
the
other
the
negative voltage
for
the
DC
output
stage. A
portion
of
the
negative voltage is stabilized
by
mea
ns
of
a
Zener
diode
and
supplies
the
negative
reference
voltage
for
the
bal
anced
servo
sy
stem
.
100 mV Ref.
The
input
reference
voltage
("100 mV Ref.")
for
sensitivity
calibration
of
the
Recorder
is developed
across
the
transformer
winding used
for
the
24
volts rectifier,
the
voltage being
amplitude
limited
and
stabilized
by
means
of
a
zener
diode. By
this
means
a
square
·wave signal is produced
and
the
input
reference
voltage will
vary
less
than
1 %
for
a
10
% variation
in
the
mains
.
Mains
Frequencies
and
Voltages.
The
apparatus
should
be
operated
from
a
50 Hz (cis) (or 60 Hz (cis)
as
specified)
power
line.
When
changing
the
Level
Recorder
from
50 Hz (cis)
to
60 Hz (ds)
or
vice
versa,
the
only
modification
to
be
carried
out
is
the
replacing
of
the
two
nylon
gear
wheels
"I"
and
"2"
by
oth
er
s (See
Fig
. 1.6).
For
more
details,
see
part
Op
era
tion,
page
37.
Adjustment
can
be
made
for
main~
voltages
of
100-
115-127-150
-220
and
240
volts
by
means
of
a Voltage Selector
on
[be
top
plate.
The
power
consumption
is 115 W
(1
45
W
with
motor
running)
.
If
the
apparatus
is to
be
oper
ated
from
an
acc
umulator
or
from
other
types
of
DC supply, the
use
of
a DC/AC
converter
(for
50
or
60 Hz (cis)
resp
ectively) is nece
ssary
.
In
these
circumst
ances
it
should
be
noted
that
the
accuracy
of
the
various
mechanical
speeds
is de
pendent
on
the
fr
e
quency
of
the
power
supply
in
use.
*)
If
the
Level Recorder is also used to control
the
filter switch of the Spectrometer Type
2112,
the
Band·Pass
Filter
Set
Type
1612,
or
the
Turntable
Type
3921,
otber
external
loads must
not
load
the
24
volts supply by
more
than
50
rnA.
19
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