HP 5528A User Manual page 338

Laser measurement system
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Madel
5528A
Appendix B: Measurement
Considerat ions
In
the caliper
examp le
(Figure
B-4),
the angular
offset
in the measurement system
is
5
arcmin, and
the
linear
offset
between
th
e
measurement
axis and the scale axis
is
50
mm
(2
inches)
.
The
error
due
to
the offset
between
the measuremenl
ax
is
and
the
sca
le
axjs
ca
n
be ca lcu lated as
-
5
X
10-
6
.
60
arcsec
error
=
50
mm
x
x
5
arcmm
x
arcsec
arcmin
=
50
x
5
X
10-
6
X
5
x
60
mm
=
75.0
X
10-
3
mm
=
0.075
mm
(0.003
in
)
By
minimizing the
offset
between the measurement
and
scale
axes,
the
error
is signifi cantly
reduced
.
For examp le,
if
the
offset
di
stan
ce
is
10 mm
(0.4 inch)
instead
of 50
mm
(2
in
ches
),
Iheerror
in the
reading
du
e
10
Abbe'
offset
error
is
-
5
X
10-
6
error
=
10
mm
X
X
300
arcsec
arcsec
=
10
X
5
X
10-
6
X
300
mm
=
15.0
X
10-
3
mm
(0.009
mm
)
=
0.015
mm
(0.0006 inch
)
II
may
be worthwhile mentioning
here
that
a
mi crometer
would n't
be
subjeclt
o
Abbe'
offset
error,
sin
ce
its measurement
axis
and its
scale axis are the same.
Co
nsider
checking the posi tio
nin
g accuracy of a
toof
on
a
mill. To minimi
ze
the
effeCI of Abbe'
offset error o
n
your
measu
rement
, you shou
ld
set
up the laser
so
that
the opt
ics
will
provide
the
exact
inform ati
on on
how the
tool
is
moving
.
The
ca
li
brat
ion
axes shou ld be
located in
th
e most critica
l
positioning
area
of
the
machine's
working
area
.
Once compensated. the machine wi
ll
position
accurately along the
ca
libration
axes.
The
wo rst accuracy will
be
at
the
greatest Abbe' offsets
from the calibration
axes.
8-
5

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