JDC Electronic SA Geos 11 - Manual (Page 22)

The tendency is displayed using 63 values. The first 3 values show the
variations in relation to the current pressure, the next 46 values in
relation to the last measured pressure on the hour, and the last 14 in
relation to the last pressure read at noon.
To view the tendency (only if the special mode is enabled, please refer
to Section: ‘Enabling a Special Mode’): display the barometric tendency
mode, select the middle block (it flashes), then by pressing briefly the
button, access the screens showing the tendency (the signs and will
show you which way the data is displayed, whether in increasing or
decreasing order; change the order using the
button). The last shift
displayed becomes the default shift in the display, and will therefore
appear next time the ‘Pressure Tendency’ special screen is accessed.
Examples of tendency display screens
Examples of display screens in relation to tendency at 11:25 on May 1
st
,
with a current relative pressure (QNH) of 1010.8.
The pressure displayed is the current pressure. The instrument
compares the current pressure (1010.8) with the pressure
recorded 25 minutes ago. This shows, as a result, that in the time
span of 25 minutes, the pressure has dropped by 0.2 hPa. If the
time was 11:43, the instrument would display -43 ', etc.
The pressure displayed is the pressure taken 1h and 25 min ago,
or the pressure read at 10:00. The instrument compares the
current pressure (1010.8) with the pressure recorded 1h and 25
min ago and displays the difference. This shows that in the time
span of 1h and 25 min the pressure has dropped by 0.5 hPa. If the
time was 11:43, the instrument would display:
-1h4, etc.
The pressure displayed is that of 3 hours ago, i.e. the pressure
read at 08:00. The instrument compares the last pressure read on
the hour (here, the pressure measured at 11:00, 1011.0) with that
taken 3 hours earlier and displays the difference. This shows that
the pressure has dropped by 0.8hPa in the time span of 3 hours.
The pressure displayed is that read 24 hours ago, i.e. the pressure
measured at 11:00 the day before (April 30
th
). The instrument
compares the last pressure read on the hour (here, the pressure
measured at 11:00 on May 1
st
, 1011.0) with the pressure
recorded 24 hours earlier and displays the difference. This shows
that the pressure has dropped by 0.4 hPa in 24 hours.
22