Delta Electronics SS1-UM-1.05 user manual Measuring Leaf Area Index without a Beam Fraction Sensor

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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.

SunScan User Manual v 1.05

SunScan Tutorial • 23

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Contents SS1-UM-1.05 SunScanCE conformity CopyrightAcknowledgements TrademarksContents Technical Reference section Menus and Screens More Psion and file handling notesMeasurement options LAI theoryIndex AppendicesOrganisation of this manual How to use the manualsIntroduction SunScan Canopy Analysis SystemData Collection Terminal Field accessoriesSunScan probe Beam Fraction sensorWorkabout and SunScan probe Getting StartedPreliminary checks Checking the Workabout hardware What the s/w does Installing the SunData s/w in your PCInstalling the s/w SunData s/w DisketteRunning SunData Setting up your PCs COM portWorkabout to PC Communication checksSunScan probe to PC Running SunData in Windows Working with the Workabout SunScan TutorialAbout this tutorial Starting SunData in the Workabout What to do if you get lostStarting the PC software Using a PC instead of the WorkaboutThis page is intentionally blank Working through the menu options Setting up a measurement sessionHot Keys File Saving Taking readings Using the Emulator modeWithout a Beam Fraction Sensor Connecting the SunScan probeConnecting the Beam Fraction Sensor Measuring Leaf Area Index without a Beam Fraction Sensor Averages Reviewing your data fileTo the PC Transferring the data file to your PCFrom the Workabout Initiating the file transfer from the Workabout Meanwhile, on the PC Conclusion of the Tutorial RS232 communication problemsSunData Screens on the Workabout File SettingsMenus and Screens Utils ContdQuit Navigating the Psion directories and screens More Psion and file handling notesNavigating Psion directories and screens Workabout User GuidePsion subdirectory usage in file select dialogs Flashcards reformatting Re-installing the SunData application iconDeleting unwanted Workabout files Data memory management Configuration and data file handlingSunData Configuration files Data files Default .cfgCreating a configuration file Restoring a configuration.CSV file Displaying data files on your PC.PRN file Data file layouts and data groups Page Above-canopy reference requirements Measurement optionsExperiment design Canopy type and LAI estimates Canopy Sampling volumeCanopy type and BFS practicalities Planning for the sun’s position Preferred light and weather conditionsAbsorption Advice on Absorption and Eladp valuesSetting Eladp Estimating Eladp in the field Relationship between Mean Leaf Angle and EladpLAI, PAR and All displays Workabout setupSunScan System Measurement modes Autolog function Levelling the probe Measurement procedures in the fieldProbe handling in the field Probe GO buttonWorkabout Using the tripodBFS handling in the field Use of the tripodExtension cables, and the location of the BFS Finding North, and setting the shade ringLevelling the BFS Recalibrate option PAR calibrationsFactory light calibration Checking the probe/BFS matchingComparing the calibration with other PAR sensors Routine maintenance and cleaningRestoring the factory calibration Effect of the shade ring on the BFSSunScan probe and Beam Fraction Sensor Environmental and moisture protectionIngredients of the LAI computation method LAI theoryTheory versus reality Derivation of Wood’s SunScan canopy analysis equationsMajor assumptions Transmission of Diffuse Light Beers law for canopy absorptionCampbells Ellipsoidal LAD equations Transmission fraction τ Is given by I/I0 Diffuse light transmission cosine corrected sensor Modelling the canopy transmissionDetail Diffuse light hemispherical response sensor Functions used to model canopy transmissionAccuracy of LAI calculations Diffuse light cosine response sensorExp 0.1 . x . atan 0.9 Atan L Q Spher Modelling incomplete PAR absorption and scatteringSummary Scientific referencesCalculating zenith angles Jones, Hamlyn G Plants and Microclimate second edition. CUP SunScan probe batteries Maintenance and repairTechnical Reference section Checking the batteriesChecking the desiccant Factory calibration method Re-setting the factory calibrationChecking the PAR calibration While running SunData TroubleshootingProblems running the SunData application Psion WorkaboutInsufficient power to write data reported Technical Support Data Collection Terminal type DCT1 Psion Workabout SpecificationsSunScan Probe Type SS1 Beam Fraction Sensor type BF1Logging Cables Carrying Case type SCC1Telescopic Tripod type BFT1 Spares Kit type SPS1Spectral response PAR PerformanceSunScan system cosine response Cosine responses of probe and BFSLogging the probe as a Linear Quantum Sensor AppendicesLogging the Beam Fraction sensor Revision History Upgrading the SunScan systemSunData PC s/w Workabout SunData s/wWorkabout Remote Link File transfer between Workabout and PCChoice of different programs PsiWinSlink and Rcom Example using SlinkDrives on the PC are referred to as REMA, Remc REM = remote Documentation of Rcom and Slink Example using RcomSending a file to a serial printer Using the Workabout Comms applicationAlternative file transfer mechanisms Sending a file to a Communication programGlossary Page Accuracy IndexIndex Field use 39, 46, 48, 50, 51, 58