Skywatch Xplorer, Owner'S Instructions Manual

Page: 24 / 100

24
8. Mode for measuring the wind speed with display of relative and absolute pressure
WHICH MEANS : The instrument offers 2 modes for displaying pressure: QFE pressure and QNH pressure. These two abbreviations (QFE and
QNH) are taken from the famous “Q” code. This code was instituted by the London conference of 1912. It is made up of a list of three letter
indicators, valid for all the countries of the world. Intended mainly for telegraphic and radio-telegraphy transmissions (in Morse) it is made up of
a list of abbreviations, using three letters to summarise without ambiguity phrases, questions or responses which would take too long to
formulate in clear text, thus eliminating the risks of errors arising out transmission, reception, language and interpretation.
The “Q” is still widely used in our day by ships and amateur radio enthusiasts. It is still official usage in radio telephony. The aeronautical world
does not use all of it, but regularly uses part of it.
CODE MEANING
QFE Atmospheric pressure at ground level, also known as absolute pressure.
QNH Atmospheric pressure obtained by calculation at sea level in standard atmospheric conditions,
also known as relative pressure.
This is the pressure mentioned in meteorological bulletins or on the television.
Choice of the unit :
If the button is kept pressed down for at least 4 seconds the units start to pass by, and you have the possibility of choosing between the
following units: hPa (hecto Pascals) and inHg (inches of mercury). When the unit of your choice appears, release the button. This validates the
unit of measurement and the instrument goes back to the mode wind / relative pressure (QNH).
Display of absolute pressure (QFE) :
Keep the button pressed down for approximately 2 seconds and at the very moment when the indication
(QFE) is
displayed in the large digits, release it. The instrument then goes into the mode for displaying absolute pressure. To quit this
mode, press once on the button, and the instrument returns to the mode wind / relative pressure (QNH).
Calibration of relative pressure (QNH) :
Hold the button pressed down for approximately 3 seconds, then release it at the moment when
is displayed on the large
digits. Then the adjustment (increase/reduction) is carried out in the same way as for the calibration of altitude, see section 7
(altitude calibration).