SunScan User Manual v 1.05
SunScan Tutorial
••••
23
By now you may have accumulated quite a lot of readings in
Data.PRN
the default
data file. There is no harm in this, but you may want to put further test results into
new file, or maybe try out a
.CSV
file. If so, follow the Data Storage instructions a
few pages back.
Measuring Leaf Area Index without a Beam Fraction Sensor
This is the most complicated of the combinations of probe and display settings. The
Measurement Options
sections discusses in detail the conditions for which it is
possible and desirable to make this measurement.
♦
set the
Ext sensor:
to
none
.
The
Next Reading
screen now includes
extra options for reading
INCIDENT
and
B FRAC
- and it won’t let you proceed
with a
READ
until you’ve taken these
readings.
♦
Highlight
B FRAC
and press
Enter
.
Hold the probe level above the canopy as
before, but now cast a small shadow over
part of the probe. Don't hold the shade too
close to the probe - otherwise it will cut
out some of the diffuse light as well.
SunData looks at the readings from the
photodiodes and uses the lowest value to
calculate the
Diffuse
component of the
incident light. It uses the highest
photodiode values to calculate the
Total
incident, and uses these two values to
calculate and display the
Beam Fraction
:
Note: SunData uses this value for the Beam Fraction to increase the accuracy of
the calculation of Leaf Area Index, as explained in the LAI Theory section.
However, this is a secondary effect, and you should not worry unduly about the
second decimal place for the Beam Fraction value.
♦
Press
Enter
or the red button to
STORE
the Beam Fraction reading.
You can now continue to take readings with the probe and display the LAI as before
- that is, until the light conditions change, when you will need to retake the Beam
Fraction readings. If you wish to recheck only the incident light reading, you can do
so as follows:
♦
Hold the probe level above the canopy, and make sure as little as possible of your
own outline is being seen by the probe.
♦
Use the
←
←
←
←
→
→
→
→
arrow keys to highlight
INCIDENT
, and press
Enter
.
SunData will display the reading from
the probe:
♦
Press
Enter
or the red button to store
this as the Incident PAR reading.
