BRUEL & KJAER 4292 Instructions And Applications page 21

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networks) of network the requirement that eR
~ec
will no longer be ful-
filled. For this reason the . 4292 employs three separate networks for
velocity measurements. The networks have lower limiting frequencies of
1 Hz, 3 Hz and 100 Hz respectively and each has an integration slope of
20 dB/decade. For measurements a net\lvork should b.e chosen which has a
lower limiting frequency equal to or less than the lowest measurement
frequency of interest. This ensures that signals with frequency component
equal to or greater than the lowest frequency of interest are correctly inte-
grated.
For displacement measurements, six double RC integration networks
similar to that shown in Fig.4.6 may be selected using the INTEGRATION
SWITCH. These networks have lower limiting frequencies (-14 dB point on
characteristics) of 1 Hz, 3 Hz, 10 Hz, 30 Hz, 100 Hz and 300Hz respective-
ly and each has an integration slope of 40 dB/decade. The frequency and
phase characteristics of the displacement networks are shown in Figs.5.9
and 5.10.
R
R
CI
O:put
Input
0
671'256
Fig.4.5. Schematic of an R-C integration network used for displacement
measurements
For acceleration measurements there is a position on the INTEGRA-
TION SWITCH where the integration networks are bypassed and the output
from the 0 to 20 dB Amplifier is applied via a resistor to the output of the
preamplifier, which is at pin 5 of the PREAMPLIFIER PLUG. The resistor
protects the amplifier against short circuit of its output. In the "velocity"
and "displacement" modes, the integration networks provide short circuit
protection of the amplifier.
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