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5
1
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CERTl FICATE
of
CAlI
BR
ATlON
Absolute Calibration
by
Laser-Interference
(Estimatod
Error less
than 0 .5
%)
(
Accelerometer Reference
Normal Type 8305
S
Serial No
..
.f?0<;."18.7..
,
..
Reference Sensitivity
at
160
Hz and
':<'3
0
C: .
!.-?3f:
pC/g
Frequency Response
•
Red
Hn
e
..
3
gnlmmes
lo
ad
1
fBI.ct1
Green
line '"
40
grammes lo
ad
Bl ack li ne
..
20
gram
m
es
1
O«t
"
-,
200
Hz
500
1000
2000 Hz
5000
10000
20000
40C
pO
D
A
B
C
lero
Level
:
(1612/21121
A
B
C
Lin
The frequency response
curves are obtained w ith the
base mounted
on an
Exciter
and
with
a load applied
to
the
top.
The
load acceleration
is
kept
co
nstant
.
Mnlm-um
Trwt.".,aa
s..,.III.lIy at 30 Hl
.
io..
'I,
A~I.'o"'.I.'
C.~dl'"e.t
.
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vm
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f.1:r. .
Mal.,lal
: S lein l,1'$
Sleel
'or
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n
. ccelerelion
dlre
c ted
1
10
m
Ul. bll!e in
\o
,he
Mountlrrg
Th,.
.d
: I
Q·
32
VNF
·
2B
body
01 the
9ccelelomete
l
.
~
Pol.rlly
I~
neg!lllve
on the
e !H
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01
the
co
nn
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COn"a Clo
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10
32
UNF-2
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Errvlron~,.I
:
Indlvldua! T.mp.,.atuTa
SenaUl vl
t)' Error
In
dB
rel
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Iha Flalerence Valua •
.
(All ......
Ided
."eI
gl_
10 ,.,.l
ei
d,ll
u,;on
,..11
Humidity
:
He rmel
lc ally "IIIad.
Mal(.
T.~raol\.l(.
:
2000C
0
1
3
92°F
Mal(.
Sho~
"'ccalaution
:
1000
Il
•
MagnetIc
a.tI./tIvl
t)'
:
(5IJ...4OO
Hl)
<
0.1 g lkgouu
"'cou,'lc
a-mvlty
:
.
EQUn.""1
g.1
164
dB
SPL
<
0 .03
•
Be..
SI'lln
s.nal1lvlty:
<
sx
10"
'
pl", ,'.
a/n
(i
n
pll ne
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1
the
bele)
•
Tamparature Tran.'.,,'
S.",III",ty:
<
I
g/
-
C
(Prel!lmp.
2621!1
LOw
Lim.
Fr~
.
.
0.3
Hl)
<
0.1 g/g
c
(Praamp.
262'6 Lo ....
LIm.
Freq
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H~)
Fo
r lunhe'
Inl
o/mat lo" tee In'1
fut tio
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boo k.
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•
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T his
Qll
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bt
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t
iOn
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~
traceabre
l
O
the
Nationa
l
Bureau
o
f
Sta
nderds
Washington
D.C.
19
.n?.
~ :
~::~::::~~,--y
-;~:~~:=JJ
Fig.
7.14.
Calibration
chart
for
an Accelerometer
8305
7
.
3.4.
Cross-Motion
Although
a
great deal
of effort
has been put
into
making the motion of the Type 48
1
5
Head rectilinear
,
it would be impossible to
eliminate
all the cross-motion.
Fig .7.16 shows plots of
cross-motion
vs
.
frequency in
two mutually
perpendicular direc
tions
for a typical Type 4815 Head. The
cross-motion is
less than
3%
up
to 2 kHz and
,
with the
exception of
one sharp peak at 3,5 kHz it remains below
10%
for the rest
of
its
range.
7
.
3.5
.
Errors in
C ali
b
ration
The important question which
comes
up
w
hen
using
a calibration
standard
concerns
the
error introduced
by
the standard itself. If a
compressor
loop is used
,
the frequency re
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