SV SLA-PA201, Руководство пользователя

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78
leads directly to the differential operator
dt
, which may be approximated by
t
Δ
in a digital
realization of the weighting if the sampling interval
t
Δ
is small enough.
NOTE 2. Frequency weighting
b
W
is considered to be the appropriate weighting curve for
z
direction comfort in rail vehicles.
b
W
is defined in BS6841:1987, and is equivalent to :
( ) ( ) ( ) ( ) ( )
1.024
h l t s
H s H s H s H s H s
= ⋅ ⋅ ⋅ ⋅
Where the parameter values
1
f
to
6
f
and
4
Q
to
6
Q
for
( )
h
H p
,
( )
l
H p
,
( )
t
H p
and
( )
s
H p
are :
1
0.4 f Hz
=
;
2
100 f Hz
=
;
3 4
16 f f Hz
= =
;
4
0.55 Q
=
;
5
2.5 f Hz
=
;
5
0.9 Q
=
;
6
4.0 f Hz
=
;
6
0.95 Q
=
NOTE 3. Parameter values in [Table 1] define exactly the frequency weighting
k
W
,
d
W
,
t
W
,
c
W
,
e
W
and
i
W
according to ISO2631-1:1997.
NOTE 4. Frequency weighting W.B.Combined and
h
W
,(formerly H.A) are unchanged by this
amendment. The parameter values in Table 1 are chosen to reproduce the weighting curves of ISO
8041:1990 using formulae of ISO2631:1997.
Above analog frequency response function is transferred to digital frequency response function by
bilinear transformation method which is below :
1
1
1
2
1
s
z
s F
z
−
−
⎛ ⎞
−
=
⎜ ⎟
+
⎝ ⎠
<Fig. 1 Highpass Filter with 0.7943Hz Cutoff>