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METER ACCUPAR LP-80, Manual

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METER ACCUPAR LP-80 Manual Download Page 49

45

LP-80

REFERENCES

Bonhomme, R., Varlet-Grancher, C. and Chartier, P., (1974). The use of hemispherical photographs 

for determining the leaf area index of young crops.  Photosynthetica , 8 (3), pp. 299–301. 

Campbell, G.S., (1986). Extinction coefficients for radiation in plant canopies calculated using an 

ellipsoidal inclination angle distribution.  Agric. For. Meteorol. , 36: 317–21

Goudriaan, J., (1977). Crop Micrometeorology: A Simulation Study, Center for Agriculture 

Publication Documentation , Wageningen, The Netherlands. 

Lang, A.R.G., (1987). Simplified estimate of leaf area index from transmittance of the sun's beam.  

Agric. For. Meteorol ., 41: 179–186. 

Lang, A.R.G. and Xiang Yueqin, (1986). Estimation of leaf area index from transmission of direct 

sunlight in discontinuous canopies.  Agric. For. Meteorol. , 37: 229–43. 

Monteith, J.L. (1977) Climate and Efficiency of Crop Production in Britain. Philos. Trans. of the 

Royal Society London B, 281, 277–294.

Norman, J.M. and P.G. Jarvis., (1974). Photosynthesis in Sitka Spruce (Picea sitchensis (Bong.) 

Carr.) III. Measurements of canopy structure and interception of radiation.  J. Appl. Ecol. , 

12:839–878.

Summary of Contents for ACCUPAR LP-80

Page 1: ...LP 80 ...

Page 2: ...wing Data 10 2 5 Downloading Data 11 2 6 Erasing Data 12 3 System 14 3 1 Specifications 14 3 2 Components 15 3 2 1 Probe 16 3 2 2 External PAR Sensor 16 3 2 3 Keypad 17 3 2 4 Display 17 3 3 LP 80 Utility 22 3 4 Theory 24 3 4 1 Average and Intercepted PAR 24 3 4 2 Sampling for Fractional Interception 25 3 4 3 Using PAR to Determine Leaf Area Index 27 3 4 4 Extinction Coefficient and Canopy Structur...

Page 3: ...n 32 3 4 7 Zenith Angle and Equation of Time 33 4 Service 37 4 1 Calibration 37 4 2 Maintenance 39 4 2 1 Replacing Batteries 39 4 2 2 Cleaning the Probe and Controller 41 4 3 Repair 41 4 4 Troubleshooting 42 4 5 Customer Support 43 4 6 Terms and Conditions 44 References 45 Glossary 46 Index 49 ...

Page 4: ... ...

Page 5: ... maintaining and caring for the instrument The LP 80 and its accessories arrive in a durable foam padded carrying case Verify all LP 80 components are included and appear in good condition ACCUPAR LP 80 External PAR sensor 5 pin to RS 232 cable USB adapter cable USB drive with LP 80 Utility attached to manual cover 1 Phillips screwdriver The LP 80 was shipped without batteries to preserve battery ...

Page 6: ...sensor and possibly void the manufacturer s warranty Before using the LP 80 follow the recommended instructions and arrange proper protections to safeguard sensors from damage 2 1 CONFIGURING Before taking measurements configure the LP 80 date time and location to ensure accurate timestamps and measurement readings The date and time can also be changed using the LP 80 Utility Section 3 3 which aut...

Page 7: ...ter of the screen in day month year format Figure 3 Arrows appear above and below the first value indicating the value can be edited Figure 3 Date screen 9 Use UP and DOWN to change the first number Holding down the arrow buttons will scroll quickly between values 10 Press ENTER to move to the next value or ESC to return to the previous value 11 Repeat step 9 and step 10 until the correct date is ...

Page 8: ...ensors in the probe Under a plant canopy radiation levels can vary so reliable measurement of PAR requires many samples at different locations An external point sensor may be used to collect instantaneous above canopy PAR measurements when sampling under or within a canopy Intercepted PAR data can be used for determining important parameters of canopy structure and for the calculation of LAI The L...

Page 9: ...this value to be accurate Section 2 1 More in depth explanations and examples of these measurements are in Section 3 4 and the Glossary The LP 80 can take measurements either manually or in unattended logging mode as explained in Section 2 2 2 and Section 2 2 3 respectively 2 2 1 MEASUREMENT TIPS ABOVE CANOPY EXTERNAL SENSOR For above canopy PAR data collection consider connecting the external sen...

Page 10: ...R readings for each of the eight probe segments by downloading the stored data to the computer The number of active segments in the probe can also be changed to limit the number of active sensors along the probe or to reflect spatial changes in the plant canopy Section 3 2 1 This is useful when evaluating discontinuous and irregular canopies SAMPLING IN ROW CROPS When using the LP 80 to measure in...

Page 11: ...the upper right section of the screen 3 To make measurements below the canopy plug in a external sensor or take an above canopy PAR reading first before the summary data can update If the external sensor is attached the LP 80 records both above and below canopy readings pressing either the UP or DOWN 4 To make measurements below the canopy press DOWN or PAR LAI in the upper right corner of the key...

Page 12: ...ding 5 Press ENTER to bring up the Save screen to save as is annotate or discard Section 2 3 Press ESC to discard the values Both options clear the screen for new data 2 2 3 LOG MODE MEASUREMENTS NOTE LAI and τ are calculated more accurately by manually sampling PAR beneath a canopy at random locations instead of leaving the LP 80 in one place and collecting data in log mode 1 Navigate to the Log ...

Page 13: ...d date of the measurement Discard return to the main screen and start over with a new reading Annotate create a file name or description Figure 11 Figure 11 Annotate screen The Annotate screen has a series of lines with a set of arrows above and below the first Old annotations will appear to be changed or deleted Use the arrow keys to select a letter or number and press ENTER to move to each chara...

Page 14: ...to the Data tab Figure 12 Figure 12 Data screen 2 Press ENTER to select View 3 Scroll through the list of saved tests using UP and DOWN Figure 13 Figure 13 View data summary screen 4 Press ENTER to select View Each entry shows the details of the saved measurement Figure 14 Figure 14 View data detail screen ...

Page 15: ...limited csv 9 Click Save to download A progress bar shows the status of the download process 10 Press Cancel to cancel the download at any time The software will not save any downloaded data 11 When the download is finished a prompt will ask to erase the data on the LP 80 12 Select the desired response 13 Navigate to the saved file location and open the file to view the data Data are organized in ...

Page 16: ...ecord ID RID of the first raw record associated with the summary record Any record between the RawRID and the RID of the summary record is also associated with the summary record Data can also be downloaded through the LP 80 or a terminal program if the LP 80 Utility is not functioning properly Contact Customer Support for more information 2 6 ERASING DATA Data can be erased using the LP 80 or the...

Page 17: ...e Data tab will reappear To erase all stored data using the LP 80 Utility 1 Make sure the LP 80 is properly connected to the computer 2 Click Erase in the lower left of the screen or go to File Erase Data A confirmation dialog box will appear 3 Click OK to continue Click Cancel to return to the main screen A progress bar will appear on the main screen indicating that data is being erased ...

Page 18: ... s Resolution 1 μmol m2 s Accuracy 5 Unattended Logging Interval Between 1 and 60 min user selectable PHYSICAL SPECIFICATIONS Controller Dimensions Length 15 80 cm 6 20 in Width 9 50 cm 3 75 in Height 3 30 cm 1 30 in Weight 0 55 kg 1 21 lb with batteries Probe Dimensions Length 86 5 cm 34 06 in Width 19 0 cm 0 75 in Height 9 5 cm 0 38 in External Sensor Dimensions Diameter 24 0 mm 0 94 in Height 2...

Page 19: ...ter Interface Locking 5 pin sealed circular connector to RS 232 cable COMPLIANCE Manufactured under ISO 9001 2015 EM ISO IEC 17050 2010 CE Mark 3 2 COMPONENTS The LP 80 is a menu driven battery operated linear PAR ceptometer used to measure light interception in plant canopies and to calculate Leaf Area Index LAI It consists of an integrated microprocessor driven data logger and probe Figure 16 Th...

Page 20: ...g from the base and continuing up the probe to the tip Section 2 2 1 3 2 2 EXTERNAL PAR SENSOR The LP 80 has an external PAR sensor that attaches to the hole in the bubble level and connects to the port on the right side of the LP 80 It allows for simultaneous above and below canopy PAR readings without moving the LP 80 above and below the canopy The LP 80 uses this sensor to calibrate the probe e...

Page 21: ...ge numeric values PAR LAI Begins a below canopy measurement alternative when taking multiple below canopy PAR samples ESC Cancels the current PAR reading cancels out of current options and navigates to the left in the Annotation screen ENTER Saves the current PAR readings in the PAR sampling tab selects items in other tabs and navigates to the right in the Annotation screen Figure 17 LP 80 keypad ...

Page 22: ... 80 Section 2 2 The PAR tab in Figure 19 indicates that the current real time PAR level is 2 μmol m2 s an indoor measurement and that the user did not take any above or below PAR measurements If the external sensor is attached the real time PAR value measured by the external sensor also display above the real time light bar PAR data Figure 19 PAR tab LOG TAB The Log tab is used to put the instrume...

Page 23: ...eading time measurement and annotation Section 2 4 Download Select to send data to computer Section 2 5 Erase Select to delete data from controller memory Section 2 6 Figure 21 Data tab CONFIGURATION TAB The Configuration tab is a menu to alter system settings and set other parameters that affect the functionality of the LP 80 Figure 22 Configuration tab options ...

Page 24: ...ged in the LP 80 Utility Time The time must be changed prior to use to record accurate information Section 2 1 Daylight Savings Daylight savings must be toggled on or off prior to use to record accurate information Section 2 1 LP 80 uses this parameter to calculate z and Fb values When daylight savings is on the time will automatically adjust Leaf Distribution χ This selection adjusts the leaf dis...

Page 25: ... PAR and Log tabs NOTE If a segment is deactivated that segment data will record 0 Deactivated segment numbers will not be used in LAI calculation Power Filter A power noise filter value may be needed to elimate noise from AC powered light sources on sensor measurements Highlight Power Filter and use ENTER to toggle between either 60 Hz or 50 Hz NOTE North American and Asian light sources use 60 H...

Page 26: ...o be installed from metergroup com lp80 support 1 Insert the USB into the USB port 2 Open the USB drive named METER Group Inc USA 3 Move the LP 80 Utility application onto the computer s hard drive The four menus across the top of the screen change program and LP 80 settings Below is a brief overview of the options each menu contains FILE MENU Download Data Saves measurement data stored in the LP ...

Page 27: ...ime automatically when connected Error Log File Adds additional details to error log files which can be sent to METER for troubleshooting ACTIONS MENU Set Date Time Synchronizes the LP 80 date and time to the computer date and time View Information Displays the serial number firmware version firmware checksum status battery level number of stored readings in the LP 80 and current date and time HEL...

Page 28: ...full sun to deep shade over the space of a few centimeters Therefore reliable measurement of PAR requires many samples at different locations under the canopy The LP 80 calculates LAI and other attributes of the canopy structure with these measurements 3 4 1 AVERAGE AND INTERCEPTED PAR Monteith 1977 observed that dry matter production of a plant canopy is directly related to the amount of photosyn...

Page 29: ...s for near infrared radiation As a first order estimate of error assume that Equation 4 r 1 t rc trs where rc is the reflectance of the vegetation Equation 2 then becomes Equation 5 f 1 t 1 rc The error resulting from using Equation 3 is approximately equal to rc which is typically 0 05 in the PAR waveband Since the LP 80 sensors are sensitive only to radiation in the PAR waveband Equation 3 will ...

Page 30: ...ed After sufficient measurements use the displayed τ value in the lower left corner for t Equation 6 To find r Equation 7 level the LP 80 above the canopy and press UP Then invert the LP 80 at a height of 1 or 2 m above the crop canopy Leveling is not critical for this measurement since the radiation reaching the sensor is not directional Press DOWN in the PAR sampling tab Multiple readings are ty...

Page 31: ...s and K is the extinction coefficient for the canopy The extinction coefficient can be modeled in various ways If an ellipsoidal angle distribution function is assumed Campbell 1986 then Equation 12 χ χ χ Θ K tan 1 744 1 182 2 2 0 733 where Θ is the zenith angle of the sun and χ is a leaf angle distribution parameter When x 1 the angle distribution is spherical and K simplifies to Equation 13 Θ K ...

Page 32: ...LE PROBLEM 2 PAR was measured at 1 614 μmol m2 s above a pea canopy and at 80 μmol m2 s below the canopy The fraction of PAR transmitted by the canopy was therefore τ 80 1 614 0 05 The zenith angle was 30 and the Fb 0 881 The A value Equation 16 is again 0 86 χ for the canopy is unknown but unless leaves have obvious horizontal or vertical tendencies a spherical distribution or default distributio...

Page 33: ...rojected area of an average canopy element on a horizontal plane to its projection on a vertical plane See the Glossary for more discussion of χ and typical values for some canopies Figure 27 Extinction coefficient versus zenith angle Figure 27 shows the extinction coefficient plotted as a function of zenith angle for various values of x There are two important things to note First at a zenith ang...

Page 34: ...0 1 32 Linear regression gives the following values for each variable A 1 21 B 0 12 L 2 1 21 0 12 2 64 χ exp 0 12 0 4 2 64 0 9 A more precise method for finding χ is as follows Find values for χ and L which minimize τ Σ F K L ln i i 2 subject to the constraint χ 0 where τi are transmission coefficients measured at several zenith angles τi and the Ki are the extinction coefficients for the correspo...

Page 35: ... 35 τ 0 21 The χ value is 0 9 p 0 92 0 92 tan35 2 1 2 τ 0 0 21 0 79 0 29 0 τ Cover 0 1 0 29 0 71 Intercepted radiation averaged over an entire day can be estimated from Equation 23 τ f 1 d where τd is the transmission coefficient averaged over all elevation angles τd can be calculated from τ uL ln d v where u and v are functions of χ which can be calculated from χ u 1 0 33exp 0 57 χ v 1 0 33exp 0 ...

Page 36: ...ds to obtain LAI rely on the assumption that elements of a canopy are randomly dispersed in space errors in the measurement of LAI may result from a nonrandom arrangement of canopy elements This is especially true for canopies with heliotropic leaves conifer forests row crops before canopy closure or canopies which never close as in desert vegetation The degree of error in measurement is a result ...

Page 37: ...result If the only measurement of interest is interception of PAR within a canopy the apparent leaf or plant area index that is calculated through inversion will be an accurate portrayal of the canopy structure and orientation with respect to light interception In this instance while clumping effects within the canopy remain present these effects do not cause error with regard to light interceptio...

Page 38: ...approximately 7 5 to 7 5 on either side of a standard meridian but this varies depending on political boundaries so check an atlas to find both standard meridian and longitude Typically longitudes in the Eastern Hemisphere are given as negative values The Equation of Time is a 15 to 20 min correction that depends on the day of the year It can be calculated from Equation 28 φ φ φ φ φ φ φ ET 104 7si...

Page 39: ... 089 Sep 27 270 0 023 0 147 Oct 7 280 0 091 0 201 Oct 17 290 0 157 0 243 Oct 27 300 0 219 0 268 Nov 6 310 0 275 0 243 Nov 16 320 0 324 0 255 Nov 26 330 0 363 0 213 Dec 6 340 0 391 0 151 Dec 16 350 0 406 0 075 Dec 26 360 0 408 0 007 EXAMPLE PROBLEM 7 Find the zenith angle for Pullman Washington USA at 10 45 PDT on June 30 Convert the time of observation to standard time by subtracting 1 h and conve...

Page 40: ...in 0 816 sin 0 4 cos 0 816 cos 0 4 cos 0 2618 9 75 11 87 arccos 0 61 radians The LP 80 automatically determines zenith angle using the above equation and parameters Once correct values are entered in the Configuration tab Section 2 1 the LP 80 determines zenith angle without further input The zenith of the sun angle will then be calculated and stored at the end of each data set ...

Page 41: ...ic use one recalibration every 2 to 3 years should be adequate METER recommends calibrating the LP 80 to the external PAR sensor at least once per hour to maintain a stable calibration between the two sensors Use the following steps to calibrate the LP 80 to the external PAR sensor 1 Unscrew the bolt from the external PAR sensor 2 Place the external PAR sensor above the hole in the bubble level of...

Page 42: ... NOTE The PAR level must be above 600 μmol m2 s for the calibration to update In general a clear day where the sun is visible will be above 600 μmol m2 s Overcast days are typically less than 600 μmol m2 s 7 Press MENU to navigate to the Configuration tab 8 Press ENTER to select Calibration A reminder screen will appear Figure 31 Figure 31 Calibration reminder screen 9 Move out of the probe area t...

Page 43: ... for maintenance in the following areas system inspection parts replacement and instrument cleaning Replacement parts can also be ordered from METER Contact Customer Support for more information 4 2 1 REPLACING BATTERIES The LP 80 uses four standard 1 5 V AAA alkaline batteries These batteries are easily obtained and should last for at least 2 years before they should be replaced If a battery icon...

Page 44: ...ove the four screws and washers Figure 34 Figure 34 Remove screws and washers from the back of the LP 80 3 Holding the case together turn the LP 80 over with the screen facing up 4 Carefully lift the cover and rotate along the bottom to lay the front cover down Figure 35 Figure 35 LP 80 battery locations ...

Page 45: ...instruments within the 1 year warranty at no charge Repairs outside the warranty window are charged based on cost of parts labor and shipping An extra fee may be charged for rush work METER will provide an estimated repair cost if requested All LP 80 instruments returning to METER for servicing must be accompanied with a Return Material Authorization RMA number Prior to shipping the instrument ple...

Page 46: ...ading Check the zenith angle value z on the PAR screen z should be between 0 to 90 degrees If z is greater than 90 degrees the time or latitude longitude are most likely incorrect Set the date time and location correctly Section 2 1 NOTE North latitudes are positive and south latitudes are negative East longitudes are positive and west longitudes are negative Warning message Low battery Check that...

Page 47: ... either PAR or Log may be running at a time Press ENTER to stop the currently running mode and to continue with the new mode or press MENU to proceed to the next tab without changing the mode Error message No summary data The view menu only allows you to view summary records I fyou have not saved any records or if you only have saved above and below records this message will appear when trying to ...

Page 48: ...te metergroup de If contacting METER by email please include the following information Name Address Phone Email address Instrument serial number Description of the problem NOTE For products purchased through a distributor please contact the distributor directly for assistance 4 6 TERMS AND CONDITIONS By using METER instruments and documentation you agree to abide by the METER Group Inc USA Terms a...

Page 49: ... Publication Documentation Wageningen The Netherlands Lang A R G 1987 Simplified estimate of leaf area index from transmittance of the sun s beam Agric For Meteorol 41 179 186 Lang A R G and Xiang Yueqin 1986 Estimation of leaf area index from transmission of direct sunlight in discontinuous canopies Agric For Meteorol 37 229 43 Monteith J L 1977 Climate and Efficiency of Crop Production in Britai...

Page 50: ...e measurement in helping to assess canopy density and biomass The LP 80 calculates LAI based on the above and below canopy PAR measurements along with other variables that relate to the canopy architecture and position of the sun These variables are the zenith angle a fractional beam measurement value and a leaf area distribution parameter for the particular canopy Leaf Distribution Parameter χ χ ...

Page 51: ...R measurements when sampling under or within a canopy Spectral Response An ideal quantum sensor would give equal emphasis to all photons between 400 and 700 nm and would exclude photons above and below these wavelengths Quantum sensors such as the Apogee that approximate the ideal response with filters are accurate to within 3 for common light sources The spectral response of the Apogee sensor is ...

Page 52: ...ime of day and is displayed in the lower right corner of the screen when taking PAR measurements To make sure this value is accurate the longitude latitude date and time of day must be set correctly Zenith angle Elevation or altitude Zenith 0 Horizon 90 Figure 36 Zenith angle ...

Page 53: ... 9 storage 15 view 10 11 19 E Equation of Time 34 external PAR sensor 15 16 20 46 F fractional beam radiation Fb 5 46 L leaf area index LAI 4 5 20 46 leaf distribution parameter χ 5 29 46 47 LP 80 Utility Actions menu 23 download data 11 12 Edit Menu 22 23 erase data 13 File menu 22 Help menu 23 installation 22 Preferences window 22 update LP 80 firmware 24 USB 1 M measurement above canopy 7 below...

Page 54: ...20 Log 8 18 19 PAR 4 18 Save Method 9 Time 4 20 View Data 10 specifications measurement 14 physical 14 15 spectral response 47 T tau τ 5 47 terms and conditions 44 theory 24 36 canopy distribution 32 33 extinction coefficient 28 fractional interception 25 27 intercepted PAR 24 25 27 28 PAR corrected for z 30 31 z and Equation of Time 33 35 troubleshooting 42 43 Z zenith angle z 5 29 30 33 47 48 ...

Page 55: ... Pullman WA 99163 T 1 509 332 2756 F 1 509 332 5158 E info metergroup com W metergroup com METER Group AG Mettlacher Straße 8 81379 München T 49 89 1266520 F 49 89 12665220 E info europe metergroup com W metergroup de 2007 2010 2013 2018 2020 All Rights Reserved ...

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