11. SETTING ATMOSPHERIC CORRECTION
11-1
11. SETTING ATMOSPHERIC CORRECTION
The velocity of light through air is not constant and depends on the atmospheric temperature and
pressure. The atmospheric correction system of this instrument corrects automatically when the
correction value is set. 15C, and 760mmHg (56F, and 29.6 inHg / 1013hPa) is as a standard
value for 0ppm in this instrument. The values are kept in the memory even after power is OFF.
11.1 Calculation of Atmospheric Correction
The following is the correction formulas.
Unit; meter
Ka
P
t
279.66
106.033
273.15
10
6
K
: Atmospheric correction value
P
: Ambient atmospheric pressure(mmHg)
t
: Ambient Atmospheric temperature(C)
The distance L(m) after atmospheric correction is obtained as follow.
=
( 1 +
Ka
)
: Measured distance when atmospheric
correction is not set.
Example : In case Temperature +20
C , Air pressure 635mmHg,
l
=1000 m
Ka
279.66
106.033 635
273.15 20
10
6
= 50
10
-6
(50
ppm
)
L
=1000 ( 1 +5010
-6
) =1000.05
m
11.2 Setting of Atmospheric Correction Value
How to Set Temperature and Pressure Value Directly
Measure the temperature and air pressure surrounding AP-L1A beforehand.
Example : Temperature: +26
C, Pressure:760mmHg
Operating procedure Operating key Display
After pressing [F4]() key 3 times to be
function as in page 4 in distance or
angle measurement mode, press
[F3](S/A) key to set "Set Audio Mode"
.
[F3]
S/A
PSM : 00 SIG:60
PPM : 83
EXIT PSM PPM T-P
Press [F4](T-P) key. [F4]
T-P SET
TEMP : 15
C
PRES : 760mmHg
EXIT
CLR
Input Temp.value and press [ENT]key.
[Example] +26
C
Input Pressure value, and press [ENT].
Mode returns to Set Audio mode.
[Example] 760mmHg
2
6
[ENT]
7
6 0
[ENT]
T-P SET
TEMP : 26
C
PRES : 760mmHg
EXIT
CLR
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