BRUEL & KJAER 2305 - Page 77

signals. The frequency range (~overed is as for sound spectrograms previously
measured by the Audio Frequency Spectrometer. The signal levels can be
measured between 100 {tV and 1000 V (full deflection) .
ODOOODODQODO D DDODDD O OODO OC OOOOQODDOOOOOODO D OOD DO CO
........ - -- ..
~
100
-
1000
, ..
~ ~ _ A I Clio.
r---... l elA ' L....-
10000
f6183{
Fig. 6.9. Spectrogram 0/ a square-wave signal analyzed in % octave band,.
Fig. 6.9 gives as an example of the analysis of a square-wave signal.
The same type of measurement can be accomplished by an equipment COD -
sisting of the Frequency . Analyzer Type 2107 combined with the Level
Recorder. With this combination the frequency range is 20-20000 Hz (cIs),
DO Ooogo Doog 000 DOD DO 00 00 DO 0 QQ 0 DOQ 000 0 00 00 0 0 00 00000 0 0 Do 110" DOODDDODDDDOOD DOD 00 DODD 0000000000
1
r -- i · _.- -r -.--. -.
!:J . !!,
J~ r Ilj l
IJ I ~ J II
.
..
Fig. 6.10. Spectrogram of the square-wave signal resolved by a continuously
varied
narrow band of approximately 8.6 % bandwidth.
and the signal levels may be between 100 pN and 1000 V (full-scale deflec-
tion) .
In Fig. 6.10 is reproduced the spectrogram for the same signal as analysed
with the Audio Frequency Spectrometer Typp, 2112.
Dynamic Strain Gage Measurements.
In dynamic strain gage investigations it may be of interest to frequency
analyse the signal from the strain gage bridge. By employing the B & K
76