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c
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Internally Calculated
Cross-over Frequency
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Pre-set
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Cross-over Frequencies
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Frequency
851820
Fig.
4.
Test programme using steps
in
acceleration,
two
pre-set cross-over frequencies and one
cross-over calculated by the controller
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1000
dB/s
300
100
30
10
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Max. 1000 dB/s
Max. 300 dB/s
Max. 100 dB/s
5
Max. 30 dB/s
$
111
a:
0
Max. 10 dB/s
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a.
E
0
Max.
3 dB/s
9
Max.
1
dB/s
0 • 1
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Frequency
Fig. 5. Compressor regulation-speed
combinations
85181811
100
80
60
dB
40
20
0
Compr.
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Auto Range
25
20
15
dB
10
5
0
Vibr.level-
Fig. 6. Compressor LED-scale
indicating
the compression level
in
decibels
The controlled vibration-parameter
can be acceleration, velocity, displace-
ment and force.
Compression levels up to 100dB can
be attained for producing a constant
vibration-level across the entire fre-
quency range. The compressor regula-
tion-speed increases in proportion to
frequency, at a selectable rate, up to a
selectable maximum regulation-speed.
Usable combinations of regulation
speeds and compression rates are
shown in Fig. 5. A separate LED-scale
displays the compression level in deci-
bels, and is shown in Fig. 6.
If
the
compressor is not used during a test,
this display will indicate the input lev-
el. In this case the measurement will
be brought into the display range by
pressing Autorange.
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Fig. 7. Digital Stroboscope Type 4913
The compressor has a safety-control
window around the vibration level
with selectable limits from 3 to 6 dB.
If
the vibration level violates these lim-
its, the instrument will revert to
stand-by mode. Alternatively the safe-
ty control may be switched off.
In complex tests, using multi-pa-
rameter control, the compressor will
regulate each parameter to maintain
the programmed level. As a conse-
quence, at the cross-overs there may
be a step in the vibration level. For
this reason the Vibration Exciter Con-
trol Type 1053 incorporates a cross-
over safety function to avoid safety
limit violation at the cross-over fre-
quencies, which would result in test
abortion.
Automatic stroboscope control
A constant output of 7 V is provided
at the two fixed outputs. Both of these
provide the control signal for a strobo-
scopic motion analyzer, allowing visu-
al examination of vibratory motion.
The Brtiel & Kjrer Digital Stroboscope
Type 4913 enables vibratory motion to
be frozen or offset to provide slow mo-
tion examination of the structure un-
der test. The Type
4913
is shown in
Fig. 7.
Interface
A digital interface, conforming to
IEEE 488 and IEC compatible, caters
for complete remote-control of the
Type 1053, for example from a desk-
top calculator. Set-up parameters or
complete test results may be docu-
mented or stored. The stored data can
then be used to set-up the front panel
of the 1053 at a later date. The Brtiel
& Kjrer Digital Cassette Recorder
Type 7400 is particularly suitable for
this purpose.
For documentation of test-runs, the
Brtiel & Kjrer Graphics Recorder
Type 2313 can print out sets of fre-
quency, generator level and meter lev-
3
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