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which also receives a 30.75 kHz signal from the fixed frequency section. A
~ignal
of frequency 750Hz is produced, which is filtered with one of the
following bandwidths, 3.16, 10, 31.6 and 100Hz at a centre frequency of
750Hz, thus removing any high frequency component and providing the
required analysis level. The pass band levels of these filters may be adjusted
using
the potentiometers (FILTER
SENSITIVITY ADJUSTMENTS)
situated on the rear panel, see section 3. 1.4. Typical overall filter charac-
teristics are shown in Fig.5.8.
5.3.5. B
&
T Programmes
The
B
& T Programmes perm it the selection of the most suitable band-
width and effective averaging time for given frequencies or frequency ranges
in order to obtain optimized measuring conditions. In certain cases the
selection of a suitable B & T programme can decrease the measuring time
considerably, see Appendix section 9.2.
The
B
& T programme selector
(B
& T PROGRAM) has five positions.
The position "Manual" enables a fixed bandwidth and averaging time to be
selected, as indicated on the SELECTIVITY CONTROL and EFFECTIVE
AVERAGING TIME switches.
In the other positions, the bandwidth and/or the averaging time are not
only dependent on the bandwidth and averaging time switch positions, but
also on the frequency pointer position. The different bandwidth and averag-
ing time combinations and the switching frequencies are given in Tables 5.1
to 5.4.
SELECTIVITY CONTROL POSITION
Automatically selected bandwidth (Hz)
1000
Hz
3.16 10
31.6
100
316
1000
316
Hz
3.16
3.16
10
31.6
100
316
100
Hz
3.16
3.16
3.16
10
31.6
100
31.6 Hz
3.16
3.16
3.16
3.16
10
31.6
10
Hz
3.16
3.16
3.16
3.16
3.16
10
3.16 Hz
3.16
3.16
3.16
3.16
3.16
3.16
Switch-over Frequency
Hz (x1, log scale)
63
200
630
2K
6.3K
Switch-over frequencies x0.1, x1, x1 0 according to range.
Table 5.1. Selected bandwidth with 8 & T PROGRAM selector in position
"8. Var. 1". Tis as selected on the EFFECTIVE A VERAG lNG
TIME switch
51
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