Delta SS1-UM-1.05 User Manual download pdf (Page 23)

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.

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Delta SS1-UM-1.05 User Manual Page 23

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