Delta Electronics SS1-UM-1.05 user manual Preferred light and weather conditions

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This means that in strong sun (high Beam Fraction) the canopy volume sampled is fairly small and well defined. As the Beam Fraction decreases, the volume sampled increases, and has less well defined limits.

Preferred light and weather conditions

These also will significantly influence your field operations.

Limitation	Comments
Time of day	Preferably within 3 hours either side of solar noon depending on
	the location and season, to meet the next two conditions.
Solar zenith angle	Measurements are easier when the sun is high. Probe and BFS
	levelling errors become larger beyond zenith angles of greater
	than 60° , especially for LAI
Incident light level -	Preferably above about 200 ∝ mol.m-2.s-1. Accuracy degrades
absolute	below this figure.
Light level - rate of	With the BFS, avoid only the very fastest changes between bright
change	sun and cloud.
	With no BFS: slow-changing conditions needed.. For LAI, with no
	BFS, slow change of direct and diffuse components.
Full overcast, or full	SunScan LAI model copes with both, but full sun will usually give
sun in blue sky	the best results. Broken cloud is also satisfactory.

Planning for the sun’s position

The SunData software on the PC contains a useful calculator for solar zenith angles on any date, to help you plan appropriate times to make your measurements. This can be accessed from the Utilities menu Alt+Utilities, Zenith calculator. The default values are taken from the Site Settings you are currently using, but can be changed within the solar predictor without affecting any settings elsewhere in the program.

SunScan User Manual v 1.05

Measurement options • 43

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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 sensorPreliminary checks Getting StartedWorkabout and SunScan probe 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 portSunScan probe to PC Communication checksWorkabout to PC Running SunData in Windows About this tutorial SunScan TutorialWorking with the Workabout 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 SavingTaking 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 fileFrom the Workabout Transferring the data file to your PCTo the PC Initiating the file transfer from the Workabout Meanwhile, on the PC Conclusion of the Tutorial RS232 communication problemsSunData Screens on the Workabout Menus and Screens SettingsFile 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 Deleting unwanted Workabout files Re-installing the SunData application iconFlashcards reformatting SunData Configuration files Configuration and data file handlingData memory management Data files Default .cfgCreating a configuration file Restoring a configuration.PRN file Displaying data files on your PC.CSV file Data file layouts and data groups Page Experiment design Measurement optionsAbove-canopy reference requirements Canopy type and BFS practicalities Canopy Sampling volumeCanopy type and LAI estimates Planning for the sun’s position Preferred light and weather conditionsSetting Eladp Advice on Absorption and Eladp valuesAbsorption Estimating Eladp in the field Relationship between Mean Leaf Angle and EladpSunScan System Measurement modes Workabout setupLAI, PAR and All displays 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 tripodLevelling the BFS Finding North, and setting the shade ringExtension cables, and the location of 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 theoryMajor assumptions Derivation of Wood’s SunScan canopy analysis equationsTheory versus reality Campbells Ellipsoidal LAD equations Beers law for canopy absorptionTransmission of Diffuse Light 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 scatteringCalculating zenith angles Scientific referencesSummary Jones, Hamlyn G Plants and Microclimate second edition. CUP SunScan probe batteries Maintenance and repairTechnical Reference section Checking the batteriesChecking the desiccant Checking the PAR calibration Re-setting the factory calibrationFactory calibration method 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