Model
5528A
V.C .
l.
Compensation
factor
19-2
number
of wavelengths
co
unted
is mUltiplied
by
a compensation factor,
and
thi
s result is then
multiplied by
the
v
..
cuum wavelength
of
the
la
ser light (
in
appropriate units
).
That
is
-
D = N x
CF
x
Wv
where
-
D
=
Di
stan
ce
N =
Number
of wavelengths of motion
CF = the Compensation
Fa
ctor.
This
number has the format "O.999abed", where
"abed"
is
the
four~digit
compensation number you
enter
for "V.C.L". The
Compensation
Fa
c
tor
represents the ratio of the Wavelength of light
in
air to
the
Wavelength of light
in
a vacuum (
WA/Wv
l,
where
-
W,.
- wavelength in air
Wv
= wavelength
in
vac
uum
The vacuum wavelength (Wvl
is
a
constant,
and
is
" hard
-wi
red"
into
the
Measurement
Di
splay
unit's arithmetic unit. The ratio of air wavelength to vacuum wavelength (
WA
/WIII
is
a
number
that
is
always slightly less than
"one",
and
which
depends
on ambient
co
nditions.
For example, for air
temperature
of
25
degrees
C
(77
degrees Fl, air pressure 01762.0
mm
(
30.00
inches) of Mercury (
Hg
),
and
relative humidity of
50%,
thi
s ratio is equal to 0.9997329.
For
the
operating environment specified for the
laser,
no
change
will
ever occur
in
the nrstthree digits of
the ratio; therefore, these three digits are
also "hard-wired"
in
si
de the Measurement
Di
splay unit,
and
you
will
have to
enter
on
ly the last four digits of the
val
ue,
in
the
format
"abc.d"
(
in
this case,
"732.9").
NO
TE
This
value would be
entered
manually
as
"732.9 V.C.L".
COMPENSATION FACTOR FOR " STANDARD" CONDITIONS
If
you
chec
k the t
ab
les
in
this User's
Guide
section, you
will
see Ihal the
compe
n
sa
tion
va
lu
es range
from
about
"695"
to
"832" parts-per-million (
"pp
m") for metric, and about "702" to "837" ppm for
English,
and
that there
is
no
"z
ero"
va
lue. This means that you should expect 10
enter
some
co
rrection value for "standard"
con
dilion
s,
even
if
you
don',
know what they are. The following
"s
tandard"
co
nditions are assumed -
Table 19-1. "SrandlJrd" Condirions
OeK
r
iption
Metric
EnK
li
th
Air
Tcmperillure:
20
0
e 68°F
Air
Pressure (
H8
):
760.0
mm
29.921 in.
Relative
Humidity:
50%
50%
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