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Model
5528A
Straightn
ess
and
Sq
u
arcness Considerat io ns
SECTION 21
STRAIGHTNESS AND
SQUARENESS CONSIDERATIONS
CONTENTS
INTROD UCTION
CALCU
LATION
OF
SLO
PE
CALCU
LATIO
N
OF
SQUA RENESS
SQ
UA RENESS SIGN CONV
ENTION
S
INTRODUCTION
This
User's
Guide Section
provides
the
information you need in order
to
cal culate and
remove
th
e
slope from you
r
Straightness measurements
or
to
ca
lculate the Squaren
ess
between
two
axes.
This Sect io
n
will also
help
you
determine
th
e
sign
co nventions
on your
St
raightn
ess measu rements
so
your
Squareness
calculation
is correct,
whether it is done
manuallyor
automatically (using
the HP
Dimensional Metrology Analysis
System).
CALCULATION OF SLOPE
There
are
two
methods used to
remove
the
slope value
from
you
r
data. The first
method
is
ca lled
"
End
Poi
nt
Fit", and the
second is called " Least
Squ
ares
Fit".
End Point Fit Method
To
remove slope
from
you
r
measurement data,
using
the "
End
Point
Fit
"
method,
you shou
ld
-
a.
Determine the
slope
of
you
r
data by
subtracti ng
th
e
first
readin
g
from
the last, and
then
dividing by the
lengt
h
of travel of the
Optics.
m
(slope)
=
last meas urement -
fir st
measurement
lengt
h
of
travel
of O
pti
c;
b.
Identify the
equation of the
line
of
your
slope
-
Ysl
ope
=
mX
+
b,
where
-
Y wil
l
be
a calculated va
lu
e,
X
is
the
distance trave
ll
ed along
th
e
measurement path,
and
b is the fi
rst St raig htness readi
n
g.
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