When using the altimeter function, your AlpinerX becomes a barometric altimeter, displaying the altitude relative to a global mean sea level.
The latter thus calculates the altitude as a function of absolute pressure (atmospheric).
As the altitude rises, pressure drops, and vice versa.
The AlpinerX's altimeter measures the difference between absolute pressure (atmospheric) and relative pressure (relative to sea level) to display the altitude.
You can calibrate your altimeter manually or use the auto-calibration option present.
NB: The AlpinerX is aligned to QNH pressure setting.
In this instance, the pressure is 'reduced' to mean sea level, assuming ISA temperature profile from the station/airfield to MSL. An altimeter set to the airfield QNH reads the elevation of the airfield when on the ground.
Due to the use of pressure to calculate the altitude, your AlpinerX's altimeter is sensitive to variations in atmospheric pressure, i.e. in weather changes.
It is therefore not uncommon to observe altitude differences of 100m in a night.
The value displayed may, therefore, vary without the altitude having actually changed.
The barometer measure the atmospheric pressure.
As the AlpinerX uses a barometric altimeter (pressure altimeter), both functions and measurements are echoing each other.
Indeed, barometers and pressure altimeters are essentially the same instruments although they are often used for different purposes.
Please read our details on the ALTIMETER to learn more about atmospheric pressure and its impact on your measurements.
The sensor will indicate the temperature with the following allowance: +/- 2 degC max (typical +/-1 degC)
Most of the electronic components bear a commercial grade with a behaviour guaranteed between 0-40 degrees Celsius. Tests on the AlpinerX have shown that the watch still works well at -10°.
If the watch is exposed below -10 and over +50 degrees, the watch won’t break but the accuracy of the measurements is not guaranteed.
The sensor will indicate the index with the following allowance: +/-1 UV index
Altimeter & Barometer
The ATM pressure will change depending on weather conditions. The altitude is calculated thanks to this pressure. A change in altitude equals a change in the ATM pressure measurement.