BRUEL & KJAER 1617 - Analysis with Variable Averaging Time Using

The Level Recorder will start to run and will drive the recording paper forward one
complete chart length of 250 mm, so that the pen is at the start position for the
next chart. Each time the pen passes the chart position for a filter change, the Recor-
der causes a band shift in the Band Pass Filter . Simultaneously, the signal level in
the frequency band is plotted out by the Recorder pen to give a frequency spectro-
gram of the whole frequency range being scanned. At the end of the range, the Re-
corder pen is lifted, the Type 1617 shifts back to its starting frequency and the recor-
der runs forward to the starting point of the next chart.
24 . If it is necessary to change the start frequency, the paper must be moved on the
sprocket an equivalent amount to ensure that correct synchronization is maintained .
25 . To avoid disturbance from noise during filter shift, there must be a certain minimum
dwell time between filter steps at the low frequency end of the range . Suitable time
intervals occur when the following paper speeds are maintained .
Filter bands 2 Hz to 10Hz
Filter bands 10Hz to 25 Hz
Filter bands above 25 Hz
Paper speed ';:;; 1 mm / s
Paper speed ';:;; 3 mm / s
Paper speed ';:;; 10 mm / s
Correct choice of writing speed will normally require equally low paper speeds, so
that in practice there will be no disadvantage.
3.3.4. Analysis with variable averaging time using the Type 2307
In this measurement mode, which is possible when a Measuring Amplifier Type 2607
(or equivalent) is employed, band switching, paper synchronization and transport, and
Amplifier averaging times are all controlled by the programs in the Band Pass Filter.
AQ 0035
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I Level Recorder 2307 I
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Fig .3 . T O. Instrumentation using Type 2307 and Type 2607 to plot
spectrograms with variable averaging time
1. Connect the instrumentation as shown in Fig .3 .1 0, which is similar to Fig .3 .9 with
the addition of the 15-lead Connection Cable AO 0145 to the AVERAGING TIME
CONTROL
socket.
Note
that program control of the Type 2607 averaging times is only possible when it
has a ground connection with the Type 1617 . This is automatically achieved when
the Filter input and output cables are connected to the Amplifier . Internal and exter-
nal connections to the AVERAGING TIME CONTROL socket are shown in Fig .3 .8
and Fig .3.7
respectively.
2 . Adjust the Measuring Amplifier as described in section 3 .3 .11 2 with the following
changes :
25