BRUEL & KJAER 2305 - Frequency Analysis with Digital Output

and another when the last is switched out (in this case CI0), here the fast
return starts.
In Fig. 6.58 is shown a recording of measurements carried out over a longer
period of time. When the Level Recorder "Paper Speed" is known, in this
example 0.1 mm/sec, the paper can be time-calibrated, as illustrated by the
recording . The number of measuring points (strain gage bridges) in this
measurement were seven.
Frequency Analysis with Digital Readout.
The Analog Voltage Readout ZR 0021 described und er "Accessories" may be
used for obtaining information about the level of signals in digital form,
especially when linear to logarithmic (dB) conversion is desired . A dynamic
range of up to 75 dB is available. ( The Level Recorder potentiometer range) .
Fig . 6.59 shows a sketch of a set-up which will give the results of 1/3 octave
frequency analysis in digital form available on pa per tape for feeding into
for example a digital computer.
Spectrometer
Input 1:S' •
Signal ..... ~ ::: i -::
Shoft
Po s it ion
Encoder
(For pu nc hing add itional
in fo rmot io n, l!! .g. otten uot or
settings)
Fig. 6.59. Set-up tor frequency analysis in lh octave bands, with punched tape
output .
The input signal, for example from an accelerometer, is frequency analysed
with a B & K Audio Frequency Spectrometer Type 2112 and the output from
this is fed to the Level Record er Type 2305 fitted with the Analog Voltage
Readout. The output from the Analog Voltage Readout is a DC voltage
proportional to the input signal level (in dB) . This voltage is fed to a digital
voltmeter the output of which is se nt to a perfor a tor whi ch punches the
information on a paper tape.
Th e stepping pul s es from the Lev el Recorder which are used for switching
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