Page 1
l
~
Goin
Olo20d8
-40dB
BrUel & Kjcer
Adj
.
X
CopoonhOgon
y
Go
-40to-20d8
in
Adj
.
Vibration Pick-up Preamplifier
X Z
Input
Goln · Goin
v-·z-
Output
~
~
Type 2625
A fully transistorised preamplifier
of
·
modular design
measurements. Integration
are included to give an output
proportional to acceleration, velocity,
or
displacement, from an accelero-
meter input. Fixed gains,
individually adjustable gains are
available from three separate inputs.
for
vibration
networks
or
Page 2
Page 3
Vibration Pick-up Preamplifier
Type 2625
Reprint
february
1970
Page 4
Contents
1.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.
Block
Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2.
Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3.
Batt:ery Compartment
2.4.
Rear pane·l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.5.
Module System
2.6.
Input Characteristics
2.7.
Frequency Characteristics
2.8. Output Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.9.
Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.10. Distortion
2.11. Noise
3.
Operation . .
3.1.
Power Requirements
3.2.
Input and Output
3.3.
Integration Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.
Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
...................................................
.......................................................
........
..........................
...............................
....................
...
.......
........
........
.......
..................
................
0
•••••••••••••••••••••••••
....
.............................................
0
........
0 .
..
.....
0
..............
0..........
.....
. . .
•••••••••••
......
....
0 0
0 14
. 14
6
6
10
11
12
13
14
Page 5
1.
Introduction
1.1. General
The Vibration Pick-up Preamplifier Type
for
networks
tion. There are three input sockets connected to a selector switch, with individual sensitivity adjustment of each input. The two inputs not in use are
connected to ground. The function selector controls three different gain ranges
for
the three inputs: 1: Variable from
+
20
with three different
limits,
The output signal is taken from a standard microsocket
coaxial socket at the
A field effect transistor stage in the
impedance, variable from about
20
dB gain.
The preamplifier has a built-in battery compartment
may be powered by external source,
The Type
amplifier
A piezoelectric device possesses a small capacitance, which develops a
charge across
connected to a large capacitance, such as a long cable to an amplifier, the
sensitivity would be much reduced, because
of
the cable capacitance and accelerometer capacitance. The main function
of
the preamplifier is as an impedance transformer, between the high input
impedance required
quired
measurement
dB, 3: Fixed at 0 dB. The integration networks are passive
1,
3,
10,
30,
100 and 300 Hz
2625
Vibration Pick-up Preamplifier is a high
for
use with piezoelectric accelerometers.
it
when subjected to an acceleration. If the accelerometer were
for
feeding the· signal into relatively high capacitance
of
velocity and displacement in addition to accelera-
lower
frequency limits.
for
front
panel,
or
3000
for
the accelerometer, and low output impedance re-
2625
is provided with integration
-40
to
-20
dB, 2: Variable from 0 to
RC
1,
10
and
100Hz
for
velocity, and six
displacement measurements.
10-32 NF
from a microsocket at the back.
input
circuit
gives extremely high input
MQ at zero gain to about
for
battery operation or
28 V DC.
input
of
the potential dividing action
of
a cable.
networks
or
a B & K
450
MQ at
impedance
small
3
Page 6
2.
Description
2.1.
Block
Diagram
A
block
One
diagram
of
three inputs is selected by the selector switch, which also controls
of
the
circuit
is given in Fig.
2.1.
the gain setting. The input stage is a field-effect transistor, and the main
amplifier stages are followed by the integration networks which are controlled from the fro.nt panel.
Selector
2.2.
Capacitive
Switch Attenuotor
Front Panel
The front panel
Differential
Input
Stage
Amplifier
Fig. 2.1.
of
Block
the 2625 is shown in Fig. 2.2. The controls are as follows:
Output
Stage
Feedback
Adjustement
diagram
Integration
Networks
of
preamplifier
Amplifier
circuit.
Power
ACCELERATION, VELOCITY, DISPLACEMENT. This knob selects the integration networks.
In the ACCELERATION position no integrating networks are
connected. Three velocity and six displacement positions are possible, giving
lower limiting frequencies as indicated. The low frequency
limit
should be set
as high as possible to obtain the best possible signal to noise ratio.
INPUT SELECTOR. This knob has twelve positions, and selects which
3 inputs,
X,
Y
or
Z is used. The two inputs
not
in use are connected to
of
the
ground.
of
Three
whereby the gain
20
different accelerometers
the twelve switch positions are labelled
X
Gain Adj.
y
0--20
z
of
the amplifier can be adjusted individually between 0 and
dB
for
the three inputs. Thus
or
it
from a triaxial accelerometer to the same value
dB
is possible to scale the signals from three
4
Page 7
Fig.
2.2.
Front panel
of
the preamplifier.
of mV/g for each channel. Accelerometers with sensitivities from 1 to
can be scaled to 10 mV/g and those with sensitivities from 10 to
can be scaled to 100 mV/g.
Also in the input stages is a capacitive attenuator which gives
tion. This gives six more switch positions, labelled
X
Gain Adj.
y
-40
to-
z
20 dB
40
dB attenua-
10
100
mV/g
mV/g
5
Page 8
and
X
Y
-40
dB
z
giving the possibility
a fixed gain
The remaining three positions
of
- 40 dB.
of
adjusting the gain between
of
the selector switch are labelled
X
Y 0 dB
z
in which no sensitivity adjustment is possible.
-40
and
-20
dB
or
giving
GAIN. These three potentiometers are used
dividually for the three inputs, as described under
INPUT.
for connection to the accelerometer via mininoise cable . The two inputs not
in use are always grounded.
OUTPUT. There are two output sockets available on the front panel, electrically
identical.
GROUND. The small unmarked terminal is connected to the instrument chassis.
The three input sockets require miniature coaxial plugs Type JP 0012,
One is a standard microsocket, the
for
adjusting
INPUT SELECTOR.
other
a B & K coaxial socket.
the
sensitivity in-
2.3. Battery Compartment
Batteries
shown in Fig.
on the rear
for
the
instruments internal supply are kept in the
2.3. The compartment is accessible by removing the
of
the
equipment (Fig. 2.4), and sliding the top panel backwards.
top
compartment
top
screw
3 X 9 V batteries are required, size 25.5 X 48.5 mm. (IEC Recommendation
86-2.6
F 22). See specifications.
2.4. Rear Panel
The rear panel
POWER SWITCH. This connects the power to the instrument by selecting either
the internal batteries
are
labelled OFF. BATT. EXT. POWER and ZR 0024, respectively. In position
ZR
0024 the output is switched from the power amplifier to the integration net-
works, thus reducing the power requirement from
2 mA.
+ 28
V.
microsocket (centre pin positive).
OUTPUT. This is the third output socket and is electrically identical to the two
on the front panel.
of
the instrument is shown in Fig. 2.4.
or
the external supplies. Four positions are available and
+ 28
V.
7
rnA
to + 28
External power, including that from the ZR 0024 is supplied to this
V.
2.5.
Module System
The preamplifier is part
shown in Fig.
very convenient.
2.5. This system makes rack mounting
6
of
the B & K module system
of
instrumentation as
of
instrument combinations
Page 9
•
Fig. 2.
3.
Battery compartment.
Fig. 2.4. Rear
A one
tier
system contains the required combination
the
metal case KK
a
portable instrument system. Standard 19" rack mounting is simple, using
the rack mounting
A three
required
assembly again fits into the wooden case KA
tier
modular instruments , all mounted in the metal case KK
0010.
This again fits into the wooden case KA
lugs which are screwed onto the case KK
system is made up
panel
of
the
preamplifier.
of
three metal cases KK
0020.
of
modules mounted in
0020,
0010.
0010
containing the
0011.
making
This
7
Page 10
•
Fig.
2.5.
The 8 & K module system.
8
Page 11
2500
2000
1500
1000
500
"'
•
Fig. 2.6. Mounting
of
Input Resistance
0
2 4 6 8
Fig. 2.7. Input impedance as a function
10
12 14
module.
of
16
18
---:J•~
gain setting.
20
dB
Gain
.;?~7/....fL7
9
Page 12
The modules are mounted in the metal cases KK 0010 and KK
1.
Loosen the finger screw in the front plate
of
the module and slide out
0011
as follows:
the bottom plate.
2. Unscrew the feet from the bottom plate.
3.
Using the same screws, fix the bottom plate inside the case KK
4.
Slide the module on to the bottom plate and fix it with the finger screw.
Input Characteristics
2.6.
0010.
Input Impedance
This is very high because of the field-effect transistor input, but it does vary
with the gain setting, as shown in Fig. 2.7.
capacity of
frequency,
this gives f =
c., and the input resistance is R'
t,
of
~
nC.R,
".
At
20 dB gain with a source capacity
0.3
Hz.
Hence for low frequency measurements it may be
If the input is fed from a source
"'
this will give a lower limiting
of
1000
pF,
an
advantage to set the gain to 0 dB.
Input Capacitance 14
0
dB
- 2
-4
-6
-8
-10
1---
0.01Hz
-
OdB
,L
/ I
/
/
~
10dB
0.1Hz
Fig. 2.8.
pF.
-
/ ,
~dB
/
_,......,.
-
V2
odB
/
/
Amplifier
--
/
--/-20dB
1Hz
/
II
II
II
I
I '\.
I
frequency characteristics.
I I
I
OdB
I I
I_
-1~F1L~d1_
I I
I!
-150pFLood
I I
Ill
I I I l l
Ill
I I
2~
7/#
1
1000kHz
.9
!'\. "
100kHz
............
" '
'\.
20...,
OdB
'
'\.
20dB
10
dB
10
20
30
40
50
~
~
'\.
~
1Hz
!--....
r:~:--
t:=:::
.
'\
""'~~
~
1\.
"
~
~'
I'
~
~ '
\
1\
t-\
~
"'
1'\
~
~
~
~
~
~
\
10Hz
Fig. 2.9. Frequency response
~
r--..
t=:::
~'r--..
.
'\
~~
~~
~
"
!"'
~
""
~
~~
~'
I\
100Hz
\
.'i
~
'\.
~
~l'\.
~
~
~
1'\.
'!'-....~
1-Z
~
\
~
~
of
integrating
II
Velocity
Displacement 4:
~~
~
"'~
~'
II
11:
2:
10Hz
3:
100Hz -0.
5:
6:
11Hz
7: 30Hz - 1mrn.
8:
100Hz-0.1mm
9;DJHz -
~
~
'"-
~
\
"-....
~
1kHz
networks.
1~z
_I
3~/~~
-
0.3m~ec.
03m
1Hz
- 1000mm.
3Hz
-
100mm.
10mm
-
0.01mm
--
"-.....
"I'
L~7'/#'
.1
sec
.
.
.
.
10kHz
Page 13
10,-----------.-
5~----------~--~--~--~--~--~--~~~-------
()ut
\l:lltage
CRMS)
2
1----
--------l-----
1--
----------!-----------h-
--
--------
.-----------.-------
--~--~--~.._-~.-----P-.:--____;~~.._---j
--"""
------>..
;:--
...P.,,----~--~.._---j
Frequency Hz
-----
Limit
for
negligible
distortion.
0 dB gain setting
Fig. 2.10.
Output
Voltage
(RMS)
Fig.
Maximum Input
10
0.1
0.
01
2.11.
Limit
2
10
of
high frequency response
position
Limit
Signal ± 0.7 V
"ACCEL."
2
10
of
high frequency response due to
± 7 V
±
70
±
700 V at
5
power
Vat
without
~
3
10
amplifier
at
at
-20
-40
due
power
"'
"
5 10'
Freoqueoncy
.
20
dB
0
dB
dB
dB
to
capacitive
amplifier.
A
1~
"'
"
""
~
"
Hz
capacitive
gain
gain
gain
gain
Limit
distortion
0
dB
10'
loading
for
negligible
gain
setting
loading
in
of
11
Page 14
2.
7.
Frequency Characteristics
The frequency characteristics
integration) are given in Fig.
networks are given in Fig.
2.8. Output Characteristics
When the preamplifier is operated from the
and current available in position ACCEL. is
or
Displacement positions the minimum Load impedance
the high frequency performance when working into capacitive loads, as Fig.
2.10 illustrates. However, when BATT.
is taken from the
voltage and
considerably as shown in Fig.
2.9. Sensitivity
As explained
-
40
dB, and variable gains from 0 to -
sitivity
of
B & K
supplied with unit.
becomes
Sv
C1
c.
C.1
is
is
is
is
where
power
current
is ± 7 V ±
under
INPUT SELECTOR there are fixed gains
acce
·lerometers, with cable, is given in the calibration chart
If a different
the
calibrated sensitivity
the
accelerometer
the
cable
the
new cable capacitance
of
the amplifier in the acceleration mode (no
2.8.
The frequency response
2.9.
ZR
0024
the maximum output voltage
± 7 V ± 1
or
EXT.
POWER are· selected, the output
amplifier. In these positions the maximum output
2.3
rnA
thus reducing the loading restriction
2.11
.
40
dB available. The voltage sen-
cable is used, the sensitivity is changed, and
capacitance (without cable)
capacitance
used when
Sv
was measured
of
the
integration
rnA
peak. In VELOCITY
is
1 MQ. This limits
of
0 dB and
Distortion
OJo
5
(28V Power Supply}
2nd.
harmonic
3rd. harmonic
--
---
3
2
o~--~--~--~~~~~~---r=-~--+---~-4~
1
0
12
2
3 4
Fig. 2.12.
Distortion
5 6
for 0 dB
7 8 9 10V
RMS
and
20
dB gain.
Output Voltage
..;?6"7/~-o
Page 15
2.1
0.
Distortion
Distortion originating in the preamplifier is shown in Fig. 2.12,
20
dB gain setting.
2.11. Noise
The noise spectrum from
in Fig.
2.13.
Total noise in the range
scale, marked
"Lin.".
20
Hz
to
40
kHz, in 1/3 octave steps, is shown
20
Hz
to
40
kHz appears at the right hand end
Total noise when weighting networks A,
ployed also appear here .
for
0 dB and
B,
C are em-
of
the
ooooooooccccccoooooooocoooooooooooocooooocooooooo
.
lri:.!!!J•r+aoa
--~
Aeceleratton
mode
0
dB
0.
......
....
...,
......
-
~-,~
,_..,
~'-',.."'•-oo
OP1123
gain
1mV
full scole
__
__
_
__
_
___
---
__
..
15
10
_
,.,
_
10
Fig. 2.13. Inherent noise
1lO
spectrum
-ria
(1/3 octaves).
,
..
, . , , • c
CIIIDIIA I
u..
'"'
CU.
13
Page 16
3.
Operation
3.1.
Power Requirements
3 X 9 V
partment using the
The
of
instrument
JP
3.2.
The
via cables
B
identical
plug
plug type
If
will
affect
2.10.
Note
or
3.3.
When using
that
range
setting
is marked on the
batteries
external + 28 V 7 rnA
the equipment, as is the ZR 0024 which supplies +
0012 plug, available from B & K (see Accessories).
for
the
three
Types 2107/
internal
12,
supply
are fitted into the
push stud connectors as described in Section
supply
is connected to the
2603/
06
and
2801/03.
Input and Output
three
inputs
& K
accelerometer.
sockets. One
type
JP
the
cables
change, as
the
that
since
balance
require
to
the
JP
0012. The large
0018,
to
the
mentioned
high
frequency
the
out
the
miniature
accelerometer.
The
output
at
the
rear and one on the front
socket
one
of
which
input
are changed , it must be noted
in section
response, as shown in the curves
outputs
standing
are
DC voltage
coaxial plugs type
A ready made cable
is taken from one
on the
front
is supplied with the amplifier.
2.9.
Long cables on the
directly
coupled,
(...n...
13
Integration Networks
the
the
network
of
the
calibrate
To
1.
Switch
2.
Vibrate
3.
Note
of
scale
amplifier.
4.
An
velocity
placement
integration
selector
the
signal. The best possible signal to noise ratio is obtained by
low
frequency
front
the
amplifier
to
position
accelerometer
deflection
amplifier.
output
If possible,
deflection,
voltage
or
displacement
is
the
networks, Fig. 2.9 should be consulted, to ensure
switch
is in the
limit
as high as possible. (The
panel).
and accelerometer with the
"Accel."
V (volts) on indicating instrument
for
value
.
at
10 mjsec2 (1
adjust
instance
of
V volts with the network
position now means that
marked on the
correct
g).
this to some convenient
with the adjustable
front
instruments
microsocket
28
V 2 mA from B & K
Connection is made via a
JP
0012
is
supplied
of
three
are
miniature,
panel takes
it
may be necessary to
V)
present
position
panel.
the
that
at
for
low
integration
connected
gain
selector
the
top
com-
2.
at
the rear
for
connection
with
each
electrically
requiring
B & K coaxial
the sensitivity
output
will also
of
Fig. 2.9 and
block
these sockets.
the
frequency
frequency
networks:
to
output
fraction
facility
velocity
of
on the
switch
or
limit
full
at
dis-
a
14
Page 17
4.
Accessories
The following accessories are available for acce·lerometers and preamplifiers.
UA 0125 Set of studs containing
YQ
2960,
studs
1 die and 1 tap NF 10-32.
UA 0142 1 set of clamping magnets containing 5 permanent magnets
UA
0070
with isolated mounting.
UA 0129 Set of
UA 0130
AO 0038
AC 0010 Mininoise cable up to
AC 0005 Mininoise cable up to 600 ft. in one length.
1.2
1.2
20
for mounting of the plugs on cable.
m (4 ft.) of mininoise cable
fitted with miniature plugs. Individually calibrated.
m
(4
fitted with miniature plugs. Individually calibrated.
90
pF/m
or
90
pF/m
or
10
mini~ture
ft.) of mini noise cable
30
pF/ft., for operation to 100°C (212°F).
30 pF/ft.,
10
nuts YM
plugs
600ft.
for
operation
isolated studs YS
0414,
10 mica washers
JP
0012
with tools and instruction
for
operation to 100°C (212°F)
for
operation to 260° C (500° F)
in one length.
to
260°C (500°F).
0420,
10 steel
YO
0534,
Fig. 4.1. Photograph
of
UA
0129
and
instructions for mounting
0012.
JP
of
the plug
15
Page 18
16
-
oiit•r
.svrt'aceot'
Clea
!!__~
c•ntr:e·-insulation
x"osed
insulatiOilto
isgra;Miteciiatea.
l'r•vent -leakage
Page 19
Input
Resistance:
Input
Capacitance:
Frequency Range:
Input
Max.
Gain:
Noise:
Load
Output:
Harmonic
Power
Batteries:
Current
Signal:
Impedance:
Distortion:
Supply:
Consumption:
5.
Specifications
Varies from 450
at
"0
dB".
14 pF.
Ace.
Vel. 3.16
» 0.316 »
))
0.0316
Displ. 1000 mm
))
100
10
1
))
0.1
0.01
± 7 V
at 0 dB
± 700 V
± 0.7 V
± 70 V
Fixed 0 and
Variable
Max.
input
Integration
position ZR 0024).
Power Amplifier. Min. 3 kQ.
Max.
Output
Less than 1
tion.
External
internal 3 X 9 V
3 X 9
25.5
Approximately
Approximately
POWER. Internal
at
at
20
at
- 20
0
to
20
11-V
(referred
± 7 V peak, 13 V DC.
impedance
28 V DC
V.
IEC
X 17.5 X 48.5 mm.
MQ
at
m/sec
))
))
))
»
))
gain
- 40
dB
dB
gain
dB
-40
dB.
20
dB
and - 40
from
2 Hz - 40 kHz with 1 nF across
to
input).
Networks:
Min. 1 MQ, max. 150
< 30 Q.
%
with
5 V RMS
source
batteries
Recommendation
2 rnA in
7 rnA in
battery
position
position
life
20
dB
gain
1
1
10Hz-
100
1
3Hz10Hz30Hz-
100
300 Hz
to
- 20 dB.
input
at 0 dB, accelera-
(for
example ZR 0024)
(not
included).
86-2, 6 F
ZR
0024.
BATT.
..J\..
7 hours.
to
HzHz-
HzHz-
Hz-
or
3000 MQ
35kHz
10 kHz
30 kHz
30 Hz
100 Hz
300Hz
1000 Hz
3000 Hz
-10000
22,
EXT.
4kHz
Hz
pF
size
·(in
or
17
Page 20
Examples:
Manufacturer
Type
I
Union Carbide Ever Ready No. 216
Hellesen
Varta Pertrix No.
Tudor
National
Type H 10
438
No.4
T4
U-006P
Dimensions:
Weight:
Accessories
Included:
(excluding knobs and feet):
Height: 132.6
Width:
Depth:
820 g (1.8 lb.)
Two
cables AO 0037, 1.2 m
One coaxial plug JP
mm
(5.22
61
mm (2.40 ins.)
200 mm (7.87 ins.)
0101.
ins.)
(4
ft.) long.
18
Page 21
Measuring Ranges:
Depending
complete
fier,
Spectrometer
on
the
arrangement
sensitivity
or
consisting
Analyzer).
and
frequency
of
response
Accelerometer, Preamplifier
of
the
Accelerometer
Type
2625
employed. Typical
and
indicating
measuring ranges
apparatus
{Microphone
of
the
Ampli-
......
<0
*)
Ace
Type
Ace.
mm/
Vel.
mm/s
Displ."'
The
in
the
.
s2
minimum
table
Minimum
Input
4332 4333 4339 4344
4334
6
I
1
0.1 0.3
0.01
I
150
15
1.5 4.5 7.5
0.
15
0.
015
0.0015
Maximum Level:
{Input
Selector
4332-4334:
4333-4335:
4339-4343:
4344:
4338:
level is
.
Level*
selector
in
4335
18
I
3
0.03
I
450
45
0.45
0.045 0.075
0.0045
in
pos. "-40
7000
g {peak) =
10000 g {peak)=
1()()()()
g {peak) = 10.
14000
g {peak) =
2000 g {peak)= 2.1(}4
limited
by
the
(RMS Value)
pos. "0 dB"
4343
30
I
5
0.5
0.
05
I
750
75
0.
75
0.
0075
dB")
Preamplifier's
I
I
7.1(}4
10.1(}4
1(}4
14.1(}4
150
I
25
2.5
0.25
I
3750
375
37.5
3.
75
0.375
0.0375
m/sec2 (peak)
m/sec2 {peak)
m/sec2 {peak)
m/sec2 (peak)
m/sec2 {peak)
internal
noise
4338
3
0.5
0.
0.
75
7.5
0.
0.075
0.
0.
which
05
005
75
0075
00075
will
Lower
All
types
1 Hz
1 Hz
10Hz
100Hz
1 Hz
3 Hz
10
Hz
30
Hz 1 kHz 1 kHz 1 kHz 1 kHz
100Hz
300Hz
normally
be
Limiting
4332 4333 4338 4344
4334
12
kHz I 18
I
4kHz
10kHz
12
kHz
I
30Hz
100
Hz
300Hz 300Hz
3kHz 3kHz
10
kHz
at
least 6
frequency
4335
4339
4343
kHz I 3.6
4kHz
10
kHz 3.6 kHz 4.8 kHz
18
kHz 3.6 kHz
30
Hz
Hz
10kHz
than
I
the
30
100
300
dB
I
100
lower
Higher
kHz
3.6 kHz I
Hz
Hz
Hz
kHz
3
3.6 kHz 4.8 kHz
corresponding
I
100
300
4.8 kHz
kHz
4
4.8 kHz
Hz
30
Hz
Hz
3 kHz
levels
Page 22
Page 23
Page 24
ACOUSTICAL . . . .
Condenser
Piezo-Electric Microphones
Microphone
Microphone
Sound
(general
and
Standing
Tapping
Noise
ELECTROACOUSTICAL ....
Artificial
Artificial
Artificial
Hearing
Telephone
Audiometer
Audio
STRAIN .
Strain
Multipoint
Automat
Balancing
VIBRATION .
Accelerometers
Accelerometer
Accelerometer
Vibration
Magnetic
Microphones
Preamplifiers
Calibration
Level
Meters
purpose-precision-
impulse)
Wave
Machines
Limit
Indicators
Ears
Mouths
Mastoids
Aid
Test
Measuring
Calibrators
Reproduction
...
Gauge
Panels
ic
Selectors
Units
...
Meters
Transducers
B
DK-2&50
NEerum
, Denmark. Teleph.:
B & K INSTRUMENTS:
Equip.
Apparatus
Boxes
Equipment
Test
Equip.
Apparatus
Preamplifiers
Calibrators
RilE
(01)
L &
80
05 00
Capacitive Transducers
Vibration
Vibration Programmers
Vibration Signal
Mini-Shakers
Complex
Stroboscopes
GENERATING .
Beat Frequency
Random Noise Generators
Sine-Random Generators
MEASURING
Measuring
Voltmeters
Deviation Bridges
Megohmmeters
ANALYZING
Band-Pass
Frequency
Frequency Analyzers
Real-Ti
Slave Filters
Psophometer Filters
Statistical Analyzers
RECORDING ... .
Level Recorders
(strip-chart and polar)
Frequency Response
Tape Recorders
Exciter
Modulus
...
...
Amplifiers
....
Filter
Spectrometers
me
Analyzers
Controls
Selectors
Apparatus
Oscillators
.
Sets
Tracers
K\.IAC.R
. Cable: BRUKJA, Copenhagen. Telex:
5316
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