Model
5526A
V.O.
L.
Compensation
Factor
The
tables in this section indicate that the correction value to be applied
for
these
"standard"
conditions, for metric
or
Eng
l
ish
units,
is
"728.
6"
,
which
is
the
"defau
lt" value built
into
the
Measurement
Displ
ay
unit for
"V.D
.l.
".
Df
c
our
s
e,
this
va
lue is not likely to be the correct one
for
your particular conditions; the remainder
of
this User's Guide
sec
tion
prov
ides details about
how
to
make a more exact determination of the compensation
number
.
NOTE
If you
do
not u
se
an
Air Sensor ,a
nd
do
not manually enter a V.D.L.
value, "728.8" (the value
for
"s
tandard" conditions) is automati-
ca
lly u
sed.
HOW
DO
YOU DETERMINE
THE
V.O.L. COMPENSATION FACTOR?
1.
SEN
S
OR
C
ON
SIDERATIONS
To det
er
mine a V.D.l. compensation value, you must first
determine
ambient temperature,
press
ur
e,
and relati
ve
humidity.
You
should pl
ace
yo
ur
sensing devices
so
that they measure the
environment
close to the meas
ured
path.
You
s
hou
ld
also
be sure to allow enough time
for
the
se
n
so
rs
to stabilize. The accuracy
with
which you determine yo
ur
compensation
number
(and, thu
s,
the accuracy of your Di
st
an
ce
measurement) will be
no
beller than the accuracy with which you measure
your
ambient
conditions,
so
yo
ur
senso
rs should be accurate. As a guide,
an
error
of
one part-per-million wi ll
occur in the distan
ce
measurement for each error
of
-
• 1-degree Celsius
(2
degre
es
Farenheit) in air
temperature
,
or
-
•
2.5
-
mm
(0.1
inch)
of
mercury in pressure, or -
• 80%
of
the relative humidily.
2. "ABSOLUTE"
PR
ES
SURE
VER
SUS " ADJUSTED"
PR
ES
SURE
Th
e ambient pressure u
sed
in
determining
yo
ur
compensation
number
must be "ab
so
lute
"
pr
ess
ure, not "adjusted"
pr
ess
ure
(w
hich is u
sua
lly absolute pre
ssu
re that
ha
s bcen
"co
rrc
cte
d"
10
sea
level").
" Adjusted pressure",
as
defined her
e,
is the absolute pressure that
yo
u
wou
ld measure
at
a given
lo
cat
ion,
if
that location
was
at
sea
level and the weather co
ndition
s were the
sa
me. Suppose,
for
exa
mple, that you were in Denver (Colorado, U.S.A
.)
at
a time when the weather report
sa
id
the
pressure
was
"762
mm
" (
30.00
inchesl of mercu
ry
. If this were
an
"adjusted pressur
e,"
and since
Denver's
altitude is about 1.5 km (
5000
feCI
),
Ihe abso
lut
e air pressure there and then
would
be
clo
se
r to
635
mm (
25
inche
s)
of
mercury.
To
measure pressure, you need
an ab
s
olute
pre
ss
ure indi
ca
tor, which is equivalent to a barometer
that
ha
s n
ot
been co
rreoed
to s
ea
le
ve
l.
When such a
pre
ss
ure indi
ca
tor is not readily
avai
lable, you
can make a
rea
so
nable approximation to ab
so
lute pressure by reducing the adjusted
pr
ess
ure
obtained from the
nearest weather
stat
ion (
at
the local airport,
for
instan
ce)
by
2.5
mm
(
0.1
inch)
of
mercury for
ea
ch
30
metres (
100
feel)
of
altitude. ThaI is -
P
ABS
""
PADJ
-
altitude
x
2.5
PA
SS =
PA
DJ -
altitude
X
0.1
'"
100
(for metric unit
s)
(for
En
glish units)
To Next Page
Loading...
Need help?
General
