Reading Cycle; Cycle Settings Screen - Delta-T Devices AP4 User Manual

READING CYCLE

Readings are displayed on the left. A bar graph shows the percentage RH in the cup. A
tick mark below the scale indicates the set point.
Inside the box on the right, the cup temperature, leaf-cup temperature difference - δT,
and the RH are displayed.
Try to keep δT < 1°C if possible, by allowing the leaf and cup to thermally equilibrate.
Wait for the reading to stabilise. The accuracy of results also depends on any changes in
the cup temperature since it was last calibrated, so recalibrate frequently.
Automatic temperature correction is incorporated in this version (2) of the software.
See also : How the Results are Calculated, in the AP4 Technical Manual
See Hints and Tips on page 42.

CYCLE SETTINGS SCREEN

Beeping : ON/OFF
This refers to a small loudspeaker.
When ON, it goes "Beep-beep" if two consecutive readings are within 2%.
Combined with the use of the GO button on the porometer head this allows you to take
and store readings without needing to look at the screen at all.
Units
See also Resistance and Conductance Units in the AP4 Technical Manual
Pressure : hPa (mbar)
If you have a barometer, enter the actual pressure.
If not, put in the standard pressure at your altitude above sea level. Use 1000 hPa (mbar)
at sea level. Reduce this by 100 hPa for every 1000 m. The results will be referenced to
the pressure you have entered. Recalibrate if you change altitude by 1000 m or more, or if
there is an extreme change of weather.
See also Barometric Pressure on page 8 of the AP4 Technical Manual and How Results
are Calculated, page 32 of the AP4 Technical Manual.
-1
s.m
-1
s.cm
2 -1
m s.mol
mm.s -1
cm.s -1
-2 -1
mmol.m s
Resistance
Conductance
HOW TO READ
Page 31