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How does the altimeter work?
Generally, air pressure and temperature decrease as altitude increases. This watch bases its altitude
readings on International Standard Atmosphere (ISA) values stipulated by the International Civil Aviation
Organization (ICAO). These values defi ne relationships between altitude, air pressure, and temperature.
Altitude
616 hPa
4000 m
3500 m
701 hPa
3000 m
2500 m
795 hPa
2000 m
1500 m
899 hPa
1000 m
500 m
1013 hPa
0 m
14000 ft.
19.03 inHg
12000 ft.
10000 ft.
22.23 inHg
8000 ft.
6000 ft.
25.84 inHg
4000 ft.
2000 ft.
0 ft.
29.92 inHg
Source: International Civil Aviation Organization
E-48
Altimeter Precautions
•
This watch estimates altitude based on air pressure. This means that altitude readings for the same
location may vary if air pressure changes.
•
The semiconductor pressure sensor used by the watch for altitude readings is also affected by
temperature. When taking altitude readings, do not subject the watch to temperature changes.
•
Do not rely upon this watch for altitude readings or perform button operations while sky diving, hang
gliding, or paragliding, while riding a gyrocopter, glider, or any other aircraft, or while engaging in any
other activity where there is the chance of sudden altitude changes.
•
Do not use this watch for measuring altitude in applications that demand professional or industrial level
precision.
•
Remember that the air inside of a commercial aircraft is pressurized. Because of this, the readings
produced by this watch will not match the altitude readings announced or indicated by the fl ight crew.
E-50
To take a barometric pressure reading
1. Enter the Timekeeping Mode.
•
For information about changing modes, see "Selecting a Mode"
(page E-24).
2. Press B once.
The v v Mode Hand will move to BAROMETER hPa or
•
BAROMETER inHg. This indicates the currently selected
30
30
barometric pressure unit setting. For information about how to
change the setting, see "To specify altitude, barometric pressure,
and temperature units" (page E-62).
The c c Second Hand will move to 0 indicating that barometric
•
pressure reading operation has started. The reading result will be
displayed within 10 seconds.
•
If the barometric pressure differential was displayed the last time
you exited the Barometer Mode, entering the Barometer mode
displays the pressure differential.
E-52
Hand Indicators
z z Hour Hand: Points to 12 o'clock.
x x Minute Hand: Points to 12 o'clock.
c c Second Hand: Specifi es the barometric
pressure differential in the
range of ±10 hPa.
v v Mode Hand: Points to BAROMETER hPa.
Reading the Barometric Pressure
Differential Indicator
Pressure differential is indicated in the range of
±10 hPa, in 1-hPa units.
•
The nearby screen shot, for example, shows
what the pointer would indicate when the
calculated pressure differential is
approximately –5 hPa (approximately –0.15
inHg).
•
The hPa unit is always used for barometric
pressure readings. You also can read the
barometric pressure differential in inHg units
as shown in the illustration.
E-54
Operation Guide 5242
Air Pressure
Temperature
–11°C
About 8 hPa per 100 m
–4.5°C
About 9 hPa per 100 m
About 6.5°C
per 1000 m
2°C
About 10 hPa per 100 m
About 11 hPa per 100 m
8.5°C
About 12 hPa per 100 m
15°C
16.2°F
About 0.15 inHg per 200 ft.
30.5°F
About 0.17 inHg per 200 ft.
About 3.6°F
per 1000 ft.
About 0.192 inHg per 200 ft.
44.7°F
About 0.21 inHg per 200 ft.
59.0°F
Current pressure
Current pressure
greater than most
greater than most
inHg values
inHg values
recent measured
recent measured
pressure
pressure
hPa values
hPa values
30
30
c Barometric
c Barometric
Current pressure
Current pressure
less than most
less than most
Pressure
Pressure
recent measured
recent measured
Differential
Differential
pressure
pressure
Indicator
Indicator
•
Note that the following conditions will prevent you from obtaining accurate readings:
When air pressure changes because of changes in the weather
Extreme temperature changes
When the watch itself is subjected to strong impact
There are two standard methods of expressing altitude: Absolute altitude and relative altitude. Absolute
altitude expresses an absolute height above sea level. Relative altitude expresses the difference between
the height of two different places.
Height of building 130 m
(relative altitude)
Taking a barometric pressure reading
The Barometer Mode uses a pressure sensor to take barometric pressure readings.
•
The differential between two readings is also indicated.
Hand Indicators
z Hour Hand: Indicates the 100s digit value when the pressure unit is hPa, and the 10s digit value when
the unit is inHg.
x Minute Hand: Indicates the 10s digit value when the pressure unit is hPa, and the 1s digit value when
the unit is inHg.
c Second Hand: Indicates the 1s digit value when the pressure unit is hPa, and the fi rst digit value to the
right of the decimal place when the unit is inHg.
v Mode Hand: Points to BAROMETER hPa when the pressure reading is less than 1000 hPa, points to
BAROMETER 1000 when the reading is 1000 hPa or higher, or points to
BAROMETER inHg when the unit is inches of mercury.
30
Example: 920 hPa
Note
•
This watch takes barometric pressure readings in 1 hPa (0.1 inHg)
units.
•
The barometric pressure measurement range and display range are
260 hPa to 1100 hPa (7.7 inHg to 32.5 inHg).
•
Whenever a barometric pressure reading is outside the allowable
measurement range, the hands of the watches will move to the
30
30
positions below.
z z Hour Hand, x x Minute Hand, c c Second Hand: 11 o'clock
v v Mode Hand: BAROMETER hPa or BAROMETER inHg
Barometric Pressure Differential Indicator
Your watch automatically takes a barometric pressure reading every two hours (at the 30-minute mark of
evenly numbered hours). If you take a manual reading, the c c Second Hand will indicate the difference
between the last auto reading and the current manual reading. You can use the barometric pressure
differentials to predict upcoming weather trends.
Positive differential: Indicates improving weather.
Negative differential: Indicates deteriorating weather.
To show and hide barometric pressure differential
1. While a barometric pressure reading is displayed in the Barometer Mode, press C.
Pressing C while an auto barometric pressure reading is indicated will take a new manual reading
•
and cause the c c Second Hand to indicate the differential between the auto reading and the new
manual reading.
2. Each press of C at this time will cause the hands to toggle between indication of the barometric
pressure reading and the barometric pressure differential.
•
The watch maintains the last barometric pressure auto reading in memory. The stored reading is
replaced whenever a new auto reading is performed.
Note
•
The barometric pressure differential unit is 1 hPa, and the display range is ±10 hPa.
If the barometric pressure differential is outside the ±10 hPa display range, the c c Second Hand will
•
move to 11 o'clock.
Rooftop at an altitude of
230 m above sea level
(absolute altitude)
Sea Level
E-49
30
Example: 25.1 inHg
E-51
E-53
E-55
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