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AM5(e) Classic Instruction Manual
7.
IEEE NOISE WEIGHTING FILTERS FOR AM5 CLASSIC
This Section describes the filters that are supplied with the AM5
Classic. Except for the 60 Hz filter, which is common to the AM5
and the AM5e Classic, the filters described comply with the
IEEE 743-1984 Standards and are used for noise measurements
described in Section 6 (sub-sections 6.3 through 6.7). The front
panel area for FILTER is shown to the right. Default selections
are shown by shading.
NOTE: The default indication for CMSG does not apply to the
default MEASURE LEVEL FREQ selection. The CMSG
default will come on when any MEASURE noise function is
selected, then go out when MEASURE LEVEL FREQ or L/F 15 kHz are
selected. No Noise weighting filter can be selected while LEVEL FREQ or L/F 15
kHz are selected.
A low-pass filter (L/F 15 kHz) can be selected by the MEASURE key for
level/frequency measurements only. The response of this filter rolls off frequencies
above 15 kHz (refer to 7.3).
A 995 Hz to 1025 Hz notch filter is automatically switched in when measuring noise
with (1004 Hz) tone, impulse noise with tone, or signal-to-noise ratio (NOISE W/T,
IMP NOISE W/T, S/N RATIO). This filter is not illustrated.
7.1
NOISE WEIGHTING FILTERS
Noise weighting filters are selected by each press of the left FILTER key (bottom to top,
left to right). Other than the lighted LED, there are no displays or parameters
associated with the FILTER selections.
Only one noise weighting filter can be selected at a time, but the 60 Hz filter (refer to
7.2) may be selected in addition to the noise weighting filter to eliminate AC power
interference. The noise weighting selections are summarized below, and the curves for
the filters are shown in the referenced figures.
FILTER
CMSG
PGM
3 kHz
15 kHz
50 kBit
WIDE
November 19, 1997
(18-0047)
DESCRIPTION
C-Message bandpass
Program bandpass
3 kHz low pass (3 dB down
@ 3 kHz, 12 dB/octave
rolloff.
15 kHz low pass (3 dB
down @ 15 kHz, 12
db/octave rolloff.
Combination low pass and
high pass.
20 Hz to 120 kHz (-120)
20 Hz to 160 kHz (-200)
AM5 CLASSIC FILTERS
IEEE/Bell STANDARD
743-1984/41009
"
"
"
"
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Page 7-1
15kHz
WIDE
3kHz
50kBit
0 0
1 1
PGM
0 0
1 1
60 Hz
CMSG
1
0
1 1
0 0
1
0
1 1
0 0
FI LTER
CURVE
Figure 7-1
Figure 7-2
Figure 7-3
Figure 7-4
Figure 7-5
Figure 7-6
Figure 7-7
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