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5.3. HETERODYNE SLAVE FILTER 2020
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Addition of the Heterodyne Slave Filter Type 2020 connected as an external filter to the
2010 enables synchronous filtering of signals. In the example shown in Fig.5.4, filter-
ing of the compressor signal enables control of the exciter level at the fundamental fre-
quency only and allows response measurements at very low levels or in the presence of
high ambient noise signals.
The filter tuning signals for the 2010 are provided by sockets marked TO 2020 on the
rear panel of the 201 0. The connections are made between the sockets "Fixed Freq.
120kHz" on the 201 0 rear panel and "120kHz" on the 2020 rear panel, and between
"Var. Freq." on the 2010 and "120-1 00 kHz" on the 2020. The push button BFO
MODE
"Sine"
must be selected on the 2020. For further details on the operation of the
Slave Filter, reference should be made to the 2020 Instruction Manual.
Since the variable frequency output from the 201 0 corresponds to the
"x
1" frequency
range, independent of the actual frequency range selected on
the
2010, only the
"x
1"
frequency range can be used with the 2020. This corresponds to the nominal frequency
range of the 2020 (i.e., 20Hz
-
20kHz). However, as the actual frequency range of the
2020 can extend below the nominal lower limit, investigations can be carried out at
lower frequencies using the "Lin x 1" range on the 2010.
Four filter bandwidths are available on the 2020,
i.e.,
3, 16, 10, 31
,6,
and 100Hz. The
filter bandwidth may be selected manually or by remote control.
0 0
- -
Heterodyne Slave Filter 2020
Level
Recorder 2307
1
Heterodyne
Analyzer
2010
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271369/
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Fig. 5. 4
.
Example of use of 2020 and 2010 for synchronous filtering
5.3.1. Remote control of the 2020 when used with 2010
60
When the BANDWIDTH selector on the 2020 is in the position
"Auto",
the filter band-
width can be selected by grounding the appropriate pin on the REMOTE BANDWIDTH
CONTROL socket on the rear panel of the 2020. If no connection is made to this socket,
the filter bandwidth
is
automatically 3,16 Hz.
Interconnection of the REMOTE BANDWIDTH CONTROL socket on the 2020 and the
EXT. B & T PROGRAM socket on the 2010 will permit remote control of the filter band-
width switching on the 2020 according to the frequency indicated on the 2010. It is pos-
sible to connect two different pins on the 201 0 to the same pin on the 2020, and this
may be useful to synchronise the selectivity of the 2020 and the 2010, when a B
&
T
programme is used on the Analyzer. For example, if the sockets are interconnected as
shown in Fig.5.5, and the B & T PROGRAM selector on the 2010 is in position "3 (B &
T var.)" and the SELECTIVITY CONTROL is on "100Hz", then the filter bandwidths on
the 2010 and 2020 have the same value and are switched synchronously throughout
the frequency range.
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