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Internally Calculated
Cross-over Frequency
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Pre-set
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Cross-over Frequencies
~~· -----r--v~
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Frequency
851820
Fig. 4.
T
est programme using
step
s
in
acceleration,
two pre-set cross-over frequen
cies
and
one
cross-over point calculated
by the
controller
1000
Max.
1000 dB/s
dB/s
300
Max. 300 dB/s
Max.
100 dB/s
100
"0
0
Max.
30 dB/s
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30
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Max.
10 dB/s
0
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10
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Cl
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Max.
3 dB/s
a:
3
Max.
1 dB/s
0,3
0 • 1
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Frequency
Pil!
.
.' 5 .
Comoressor re{Julation sp eed
combinations
85181811
100
80
60
dB
40
20
0
Compr.
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Auto Range
25
20
15
dB
10
5
b
Vibr.
Level -
Fig. 6.
Comp;essor LED scale indicating
the
compression level in
decibels
The controlled vibration parameter
can be acceleration, velocity, displace-
ment and force.
Compression levels up to 100 dB can
be attained to produce a constant vi-
bration level across the entire frequen-
cy range. The compressor regulation
speed increases in proportion to fre-
quency 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.
The compressor has a safety control
window around the set vibration level
Fig. 7. Digital Strobos
cope
Type 4913
with selectable limits from 3 to 6 dB. If
the vibration level causes violation of
these limits the instrument will revert
to stand-by mode. Alternatively the
safety control may be switched off.
In complex tests using multi-param-
eter control the compressor will regu-
late each parameter to maintain the
programmed level. As a consequence,
at the cross-overs there may be a step
in the vibration level. For this reason
the Vibration Exciter Control Type
1050 also incorporates a cross-over
safety function to avoid safety limit
violation at the cross-over frequencies
which would result in test abortion.
Automatic Stroboscope Control
A constant output level of 7 V is
availabl,e from the two fixed outputs.
Either of these can provide the control
signal for a stroboscopic motion ana-
lyzer for visual examination of vibra-
tory motion. The Brtiel & Kjrer Digital
Stroboscope Type 4913 and Fibre-Op-
tic Light Source Type 4915 enable vi-
bratory motion to be frozen or offset
to provide slow motion examination of
the structure under test. The Type
4913 is shown in Fig. 7.
Interface
A digital interface, conforming to
IEEE488 and IEC compatible, caters
for complete remote control of the
Type 1050, e.g. from a desk-top calcu-
lator. Set-up parameters or complete
test results may be documented or
stored. The stored data may later be
used by the 1050 to set-up the front
panel. The Brtiel
&
Kjrer Digital Cas-
sette Recorder Type 7 400 is particu-
larly 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-
el at periodic intervals. It can also
print out the test parameter values.
3
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