Model
5528A
Parallelism
Measurements
14
·8
If you
don
't use
the
HP
Dimensional Metrology Analysis System, follow the instructions given
in
Sec
ti
on
10
of this User's Guide,
then
refer
to
Section
21
of this User's Guide and calculate the
slo
pe
of
your
measu r
emen
t data.
Second-Axis
Measurement
To measure
the
second
axis
, you
on
ly have to rotate
the
spindle and Straightncss Reflcdor 180
degrees
and make a
measurement.
The instructions below ind
ica
te
the
extra things you should
do
for this measurement
axis.
In
stallation and Alignment
of
Optics
ROl<lte
the
spindle
180
dcgrees. Do not adjust the tilt of
the
Straightness Reflector.
Measurement Display Settings
r:;J
~
You
must c
hange
the
Direction Sense for this second measurement. Prcss
th
e
OIR
SENSE
key.
Making A Measurement
Use
the
same instructions you did for
the
first
axis
measurement.
Calculating Rotational Parallelism
Once
you have
the
slope for
each
meas
urement
axis
(from Section 21). transl,lIe the slope values
into a Parallelism value. What you must
do
is
-
1. For
each
axis,
determine
the
angle
of misalignment (8).
This
is
done
by taking
the
arctangent of
the
sl
ope
(m) of each Straightness measurement and
muhiplying by
"3600",
to
co
nvert
to
"a
rcseconds".
8 = larctangent (m)] x
3600
(a
rcseconds)
Be
sure
your sl
ope
value
Is
dimensionle
ss,
i.e., metre/ metre or inch/ inch.
2. Add
the
angles together
and
divide by two.
Rotational Parallelism Error
;=
(
01
+ 02)12
I n
order
to
do
this,
the
first· and second·axis measurements must have deflections of the
Interferom
ete
r
produce
opposite
sign conventions when in
the
same direction.
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