Description
Both Band Pass Filters are de-
signed to operate on the signals ob-
tained from the External Filter termi-
nals of the Measuring Amplifiers,
but any input signal of approxi-
mately 1V RMS with a crest factor
less than 5 can be accepted (the
higher crest factor capability of the
Type 2606 can be used at lower sig-
nal levels). Input and output are via
coaxial B & K sockets on the front
panel, paralled by BNC terminals on
the rear.
Filter I Filter II
Centre , Centre
Frequency Frequency
Hz Hz
1/3 Octave
Bandwidth
at 3,7 dB
Hz Approx.
2
3,15
5
8
12,5
20
31.5
50
80
126
200
315
500
BOO
1250
2000
3150
5000
8000
12500
20000
25000
31500
40000
50000
63000
80000
100000
125000
160000
2.5
4
6,3
10
16
25
40
63
100
160
250
400
630
1000
1600
2500
4000
6300
10000
16000
Additional
1/3-octave
filters
in 1617
0,46
0,50
0.73
0,92
1.16
1,45
1,83
2,30
2,90
3,70
4,60
5,8
7,3
9.2
11,6
14,5
16,3
23
29
37
46
58
73
92
116
145
183
230
290
370
460
580
730
920
1160
1450
1830
2300
2900
3700
4600
5800
7300
9200
11600
14500
18300
23000
29000
37000
Tab l e 2. Filter centre frequencies in pre•
(erred series. Heavy type denotes
preferred series for full-octaves
C) Input
Overload
Warning
Input
Amplifier
8
2 Hz -
20 kHz
1/1-1/3 oct
Filter I
is)
0 I
Low Pass
ss./C
2,5 Hz -
16 kHz
1/1-1/3 oct
Filter II
4..425 kHz
4-131,5 kHz/
4:40 kHz
Front
Paver
Controls
:50 kHz
:.:i!63 kHz-
480 kHz/
100 kHz
125 kHz
160 kHz
Filter':;;:.
Selector
Filter
Selector II
V
Digital
Controller
Amplifier
Low Pass
Filter
Output
Amplifier
Output
Interlace
....•• ,•
Digital
Averaging Time;::
,?.:•..,•••••
X-Y Recorder:.
Level Recorder
Control
76,0391
Fig.1. Block diagram of the Band Pass Filters Type 1617 and Type 1618
Fig.1 is a block diagram valid for
both versions of Band Pass Filter,
where shaded areas represent fea-
tures found only in the Type 1617.
Third-Octave Band Pass Filters
The active Filter sections consist
of a matched pair of variable fre-
quency six-pole Butterworth filters
which can be electronically
switched to yield third-octave or full-
octave bandwidths. Between them
the two Filters cover the frequency
range from 2 Hz to 20 kHz centre
frequencies, with each Filter being
switched to alternate third-octave
centre frequencies in the preferred
series (see Table 2)
In the Band Pass Filter Type
1617 there is an additional set of
third-octave Filters with centre fre-
quencies between 25 kHz and
160 kHz, to extend the high fre-
quency range of the instrument.
these instruments fulfil the require-
ments of IEC 225 — 1966, DIN
45652, and ANSI S1.11-1966
Class III, which are the most rigor-
EC
Typical 8 & K
1/3 Octave Filter
\ ANSI Class III
,f0IN 45652)
0,2 0,5 2 4
Frequency relative to centre frequency f/fm „0,03j
dividual third-octave Filters used in Fig,2. Typical third-octave filter response
The filter characteristics of the in-
3
To Next Page
Loading...
