Leaf Porometer Operator’s Manual
3. The Menus
19
Remove the sensor from the leaf and wait until the bar on
the right drops below the AMB> marker (this may take a
while), at which time the “Place sensor on leaf ” screen will
reappear. Or, to reset more quickly, hold the sensor firmly,
open the sensor head, and wave in the air lightly to equalize
the humidity. Do not blow into the sensor; this can cause
inaccurate readings when the measurement begins.
Once
the ambient humidity has been reset, you will be prompted
to place the sensor head on the leaf again.
If the stomatal conductance reaches a value beyond the rec-
ommended range of the instrument(0 to 1000 mmol/m
2
s),
an “approximate” symbol will appear to the left of the read-
ing. If the stomatal conductance reaches a value greater than
or equal to 6000 mmol/m
2
s, an “infinity” symbol is shown
in place of the measurement. Most often, the excessively
high values are caused by water on the leaf surface. If you
consistently are getting high readings, check your leaf sur-
face for the presence of water.
Measurement Precautions
General Precautions
• Before using the sensor, allow it to equilibrate to the
ambient temperature. This may take 10 minutes or
longer to complete; if the temperature of the porometer
is very different from the sampling environment, e.g.
from a cool air conditioned room to a hot outdoor envi-
ronment.
• The first reading in Auto mode after the sensor has
been removed from a leaf for more than five minutes
