Agilent Technologies 8504B - Page 82

FINAL TRIM SIZE : 7.5 in x 9.0 in
P
erforming
Measurements
Setting the
Measurement
Range
Horizontal
scale
readings
depend
upon
refractive
index
The
precision reectometer's
maximum measurement
span
depends
upon
the
refractive
index of
the light
path.
The
default
horizontal
scale
corresponds
to
a
refractive index
( n
)
of
1.
(This
is
the
value
for
light
in
air
,
and
it
gives
the
precision
reectometer's maximum
range of
400 mm.)
Entering
a
dierent
refractive
index,
using
the
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
NN
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N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
NN
NN
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NN
N
N
N
N
N
N
N
N
N
N
N
N
N
REFRACTIVE
INDEX
(n)
softkey
,
changes
the
horizontal
scale but
not the
position
of
responses
on
the
display
.
Refraction
index
=
1.
Refraction
index =
1.44.
The
precision reectometer
is
designed
so
that
if
the
lengths
of
the
REFERENCE
EXTENSION and
TEST PORT
cables
are
equal,
the
rst
response
appears
approximately one
division to
the
right
of
the
display's
left
edge
in
a
400
mm
span.
(This
response
is
reected
from
the
end
of
the
TEST
PORT
cable
.)
F
or
every
28
millimeters
that
the
TEST
PORT
cable
is
longer
than
the
REFERENCE
EXTENSION
cable
,
this
response
moves
one
division
towards
the
right.
Twenty-eight
millimeters
of
actual
ber
length
has
an
equivalent
air
length
of
40
mm.
Return
to full
span with
the
press of
a
key
Y
ou can
return the
instrument to
the
full
400
nm
span
at
any
time
by
pressing 4
MENU
5
N
N
N
NN
NN
NN
NN
NN
NN
NN
N
N
N
N
N
N
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N
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N
N
N
FULL SPAN
.
Next
to
the
N
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N
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NN
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N
N
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N
N
N
N
N
FULL SPAN
key
,
you'll
nd
the
NNNNNNNNNNNNNNNNNNNNN
NNNNNNNNNNNNNNNNNNNNNNNNN
NNNN
ZERO SPAN on OFF
softkey. This softkey make the precision reectometer
into what is essentially a programmable delay line
. It sets the center setting
to the former start value and
stops the sweep (mirror movement).
3-5
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