METER ACCUPAR LP-80 Manual
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METER ACCUPAR LP-80 Manual

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  • Page 1 LP-80...

  • Page 2: Table Of Contents

    10242-12 2.28.2020 TABLE OF CONTENTS 1. Introduction ....................1 2. Operation ....................2 2.1 Configuring ....................2 2.2 Taking Measurements ................4 2.2.1 Measurement Tips ................5 2.2.2 Manual Measurements ..............7 2.2.3 Log Mode Measurements ..............8 2.3 Saving and Annotating Readings ............... 9 2.4 Viewing Data ....................
  • Page 3 3.4.5 Correction of PAR for Sun Angle ............ 30 3.4.6 LAI Measurements and Nonrandom Distribution ......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 ..........

  • Page 5: Introduction

    1. INTRODUCTION Thank you for choosing the ACCUPAR LP-80 PAR/LAI Ceptometer from METER Group. The LP-80 measures photosynthetically active radiation (PAR) and can use these readings in a model to give a leaf area index (LAI) for a plant canopy. This manual includes instructions for setting up the LP-80, verifying the calibration of the instrument, preparing samples, and maintaining and caring for the instrument.

  • Page 6: Operation

    • Transport the instrument in its padded hard-sided carrying case to prevent damage. PRECAUTIONS METER instruments are built to the highest standards, but misuse, improper protection, or improper installation may damage the 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.
  • Page 7 LP-80 Figure 2 Location screen NOTE: North latitudes are positive and south latitudes are negative. East longitudes are positive and west longitudes negative. Use UP and DOWN to highlight the desired options, and press ENTER to access the lists to update the selections appropriately. Press ESC when all displayed location information is correct.

  • Page 8: Taking Measurements

    OPERATION The system time appears in the center of the screen in 24-h format (Figure 4). Arrows appear above and below the first value, indicating the value can be edited. Figure 4 Time screen 17. Use UP and DOWN to change the first number. Holding down the arrow buttons will scroll quickly between values.

  • Page 9: Measurement Tips

    LP-80 • PAR: radiation in the 400- to 700-nm waveband, representing the portion of the spectrum that plants use for photosynthesis. • τ (tau): ratio of below-canopy PAR measurements to the most recent above-canopy PAR measurement, calculated automatically by the LP-80. •...
  • Page 10 When using the LP-80 to measure in crop rows, take measurements in a way to give a good row-to-row representation of the entire below-canopy PAR environment both under the plants and between rows. METER suggests either of the sampling regimes below, where the probe either extends from mid-row to mid-row (Figure 6) or extends from mid-row to the middle of the open space between rows (Figure 7), depending on row width and canopy size.

  • Page 11: Manual Measurements

    LP-80 Figure 7 The base of the probe is in the center of the row and the end is in the center of the open space between rows. When sampling the next row, the same orientation is maintained, giving an accurate representation of the overall area.

  • Page 12: Log Mode Measurements

    OPERATION LP-80 updates and displays the current calculated τ, LAI, F , χ , and z values at the bottom of the screen with each subsequent below-canopy PAR measurement. With each above- or below-canopy measurement, a number appears to the right of the PAR value that indicates the number of completed measurements.

  • Page 13: Saving And Annotating Readings

    LP-80 2.3 SAVING AND ANNOTATING READINGS To save a reading after taking above and below PAR data, Press ENTER. The Save Method screen appears (Figure 10). Figure 10 Save Method screen Choose to save, annotate, or discard data. Š Save: data stores with the time and date of the measurement. Š...

  • Page 14: Viewing Data

    OPERATION 2.4 VIEWING DATA To view prior test results, use the following steps: Press MENU to navigate to the Data tab (Figure 12). Figure 12 Data screen Press ENTER to select View. Scroll through the list of saved tests using UP and DOWN (Figure 13). Figure 13 View data summary screen Press ENTER to select View.

  • Page 15: Downloading Data

    LP-80 2.5 DOWNLOADING DATA METER recommends using the LP-80 Utility to download data. This function transfers all saved measurement data on the LP-80 to a computer. Connect the 5-pin connector to the LP-80. Connect the RS-232 end of the cable to an available serial port on a computer or to a USB-to-serial adapter.

  • Page 16: Erasing Data

    OPERATION • LAI: Area of leaves per unit area of soil surface. • χ: Ratio of projected area of an average-canopy element on a horizontal plane to its projection on a vertical plane. • F : Ratio of direct beam radiation coming directly from the sun to radiation coming from all ambient sources.
  • Page 17 LP-80 To return to the Data tab and leave stored data intact, press ESC. To erase data from memory, press ENTER. NOTE: This will delete all data permanently. When the process is complete, the Data tab will reappear. To erase all stored data using the LP-80 Utility: Make sure the LP-80 is properly connected to the computer.

  • Page 18: System

    SYSTEM 3. SYSTEM This section describes the specifications, components, and theory of the LP-80. 3.1 SPECIFICATIONS MEASUREMENT SPECIFICATIONS Probe PAR Sensors Range 0 to 2,500 μmol/(m Resolution 1 μmol/(m External PAR Sensor Range 0 to 4,000 μmol/(m s) (full sunlight ~2,000 μmol/[m Resolution 1 μmol/(m ±5%...

  • Page 19: Components

    Leaf Area Index (LAI). It consists of an integrated microprocessor-driven data logger and probe (Figure 16). The LP-80 displays PAR in units of micromols per meter squared per second (μmol/[m s]). The instrument is capable...

  • Page 20: Probe

    SYSTEM Figure 16 LP-80 ceptometer The LP-80 can be operated in environments with temperatures from 0 to 50 °C and in relative humidities of up to 100%. The LP-80 operates on four AAA alkaline batteries. The instrument ships with an RS-232 interface cable for downloading data to a computer. 3.2.1 PROBE The probe contains 80 independent sensors, spaced 1 cm apart.

  • Page 21: Keypad

    LP-80 3.2.3 KEYPAD The LP-80 keypad is a 7-button panel, designed for ease of use and intuitive navigability through the operating system (Figure 17). • POWER: Turns the instrument on or off. The LP-80 turns itself off automatically after 10 min of inactivity. •...
  • Page 22 SYSTEM The default screen is the PAR sampling tab with real-time PAR data displayed in the center portion of the screen (Figure 18). If the battery is low, a low-battery indicator will appear between the tabs and the current time. Figure 18 LP-80 display PAR TAB The PAR tab is the PAR/LAI sampling screen, which is used for taking measurements with the LP-80 (Section 2.2).
  • Page 23 LP-80 Figure 20 Log tab DATA TAB The Data tab is to view, download, and erase data and displays a summary of records and memory use (Figure 21). • View: Select to see reading time, measurement, and annotation (Section 2.4). • Download: Select to send data to computer (Section 2.5). •...
  • Page 24 SYSTEM This menu features eleven options: • Calibration Calibration will begin the calibration process (Section 4.1). The external PAR sensor (Section 3.2.2) will be needed to complete calibration. • Location The location must be set to the appropriate country, city, latitude, and longitude prior to use to make accurate LAI calculations (Figure 23;...
  • Page 25 LP-80 • Active Segments The Active Segments screen changes the number of active segments on the probe (Figure 24). Figure 24 Active segments screen Use UP and DOWN to set the desired active segments. The icon on the right side of the screen will illustrate the active segments as the number is increased or decreased.

  • Page 26: Utility

    LP-80 Utility can also be installed from metergroup.com/lp80-support. Insert the USB into the USB port. Open the USB drive named METER Group Inc. USA. 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.
  • Page 27 Help menu. • Automatic Clock Synchronization: Sets the LP-80 time to the computer time 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.

  • Page 28: Theory

    SYSTEM To update the firmware, use the following steps: Connect the LP-80 to an available communication port. Download the LP-80 Firmware Updater executable file from the LP-80 product website (metergroup.com/lp80-support). Click Run. If the application does not automatically ask, open the firmware updater application from the Downloads menu.

  • Page 29: Sampling For Fractional Interception

    LP-80 The incident radiation on a canopy can be (1) absorbed by the canopy, (2) transmitted through the canopy and absorbed or reflected at the soil surface, or (3) reflected by the canopy. In principle, only PAR absorbed by the canopy is useful in producing dry matter, so f should be the fractional absorption.
  • Page 30 SYSTEM Assume only t needs to be done and S needs to be measured above the crop canopy. Level the LP-80 above the canopy and press UP. The reading displayed in the upper right portion of the screen is the value for S. Measure T by placing the LP-80 below the plant canopy.

  • Page 31: Using Par To Determine Leaf Area Index

    LP-80 3.4.3 USING PAR TO DETERMINE LEAF AREA INDEX The PAR measured by the LP-80 within a plant canopy is a combination of radiation transmitted through the canopy and radiation scattered by leaves within the canopy. A complete model of transmission and scattering is given by Norman and Jarvis (1975), but it is very complex and not suitable for inversion.

  • Page 32: Extinction Coefficient And Canopy Structure

    SYSTEM The LP-80 program utilizes these equations when the instrument is used to automatically calculate LAI. With the correct local time, date, and leaf distribution parameter, the LP-80 automatically calculates zenith angle and beam fraction. It then couples these parameters with collected intercepted PAR data to determine LAI. This section describes the method of manually collecting PAR data for the determination of LAI in a barley and pea canopy.
  • Page 33 LP-80 where L is the LAI of the canopy (area of leaves per unit area of soil surface) and K is the extinction coefficient for the canopy, which depends on the leaf angle distribution of canopy elements and the zenith angle of the probe. A number of expressions have been proposed for K.

  • Page 34: Correction Of Par For Sun Angle

    SYSTEM If measurements of the transmission coefficient, τ, are made at several elevation angles, a simple method from Lang (1987) can be used. The measurements of τ are used to compute y cos ln Θ τ Θ Equation 20 These are regressed on Θ (in radians), giving a slope (B) and intercept (A). LAI is given by: Equation 21 An approximate value for χ...
  • Page 35 LP-80 τ τ τ τ Θ = Θ Calculate p from Equation ⎡ ⎤ χ + (tanΘ ⎢ ⎥ χ + (tanΘ ⎣ ⎦ If Θ = 0°, ⎡ ⎤ χ ⎢ ⎥ χ + (tanΘ ⎣ ⎦ If χ is not known, assume χ = 1. EXAMPLE PROBLEM 5 From the measurements in Example Problem 4, find the canopy cover.

  • Page 36: Lai Measurements And Nonrandom Distribution

    SYSTEM χ 0.69 0.73 0.75 0.82 0.81 0.89 0.90 0.95 0.96 0.98 0.99 0.99 Combining Equation 17 Equation 23 gives: τ τ Θ where q=uL EXAMPLE PROBLEM 6 Calculate a value for fractional daily interception for the crop in Example Problems 4 and 5. 1.033exp( 0.57 0.9) 0.80 −...

  • Page 37: Zenith Angle And Equation Of Time

    LP-80 relating to the interception of PAR at a given angle. In situ measurements of LAI using hemispherical photography were equated with this new term “effective plant area index” (L which was defined as: = ΩL Equation 24 where L represents the actual LAI (equal to a harvested leaf area measurement) and Ω...
  • Page 38 SYSTEM • D = solar declination (Equation 26), which ranges from +0.409 radians (+23.45°) at summer solstice to -0.409 radians (-23.45°) at winter solstice: arcsin{0.39785sin(4.869 0.0172 0.03345sin(6.224 0.0172 )]} Equation 26 where J is the day of the year. • 2.618 = conversion of hours to radians (Earth turns at a rate of 0.2618 radians/h) •...
  • Page 39 LP-80 Table 1 Solar Declination and Equation of Time (continued) Date Day of Year ET Hour (Radians) Apr 30 0.253 0.046 May 10 0.304 0.060 May 20 0.346 0.059 May 30 0.378 0.043 Jun 9 0.399 0.015 Jun 19 0.409 –0.019 Jan 29 0.406...
  • Page 40 SYSTEM 28, ET = -0.06 h. then gives t From Equation Equation 27 = 12 − 0.19 − (−0.06) = 11.87. Declination from Equation 26 is 0.4 radians. Substituting these values into Equation 25 gives: sin(0.816)sin(0.4) cos(0.816)cos(0.4)cos[0.2618(9.75 11.87)] arccos − Θ...

  • Page 41: Service

    PAR sensors that are used heavily, annual calibration is recommended. For periodic 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.
  • Page 42 SERVICE Figure 30 Level the LP-80 probe and external sensor Turn on the LP-80. Press ENTER to check that the PAR level meets the 600 μmol/(m s) threshold for calibration. If necessary, adjust the sun exposure of the LP-80 to meet the threshold. NOTE: The PAR level must be above 600 μmol/(m s) for the calibration to update.

  • Page 43: Maintenance

    Figure 33 Calibration Complete screen 12. Press ENTER again to save. 4.2 MAINTENANCE LP-80 may be returned to METER 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.
  • Page 44 SERVICE Place the LP-80 with the screen facing down. Use the included Phillips screwdriver to remove the four screws and washers (Figure 34). Figure 34 Remove screws and washers from the back of the LP-80 Holding the case together, turn the LP-80 over, with the screen facing up. Carefully lift the cover and rotate along the bottom to lay the front cover down (Figure 35).

  • Page 45: Cleaning The Probe And Controller

    METER repairs manufacturer defects and 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.

  • Page 46: Troubleshooting

    ENTER to continue. Error message The instrument cannot download new firmware updates. The Missing bootstrap loader! instrument must be serviced by METER. Contact Customer Support. See Manual for options. Error message Download data records to a computer (Section 2.5) and erase the LP-80 memory (Section 2.6).

  • Page 47: Customer Support

    LP-80 Table 3 Troubleshooting the LP-80 (continued) Problem Possible Solutions This screen means that the firmware was not loaded properly or an update is needed. Check metergroup.com/lp80-support if a new firmware version is Error message available. Firmware is corrupted! NOTE: Saved data records will be lost when new firmware is installed. See Manual for options.

  • Page 48: Terms And Conditions

    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 and Conditions. Please refer to metergroup.com/terms-conditions...

  • Page 49: References

    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.

  • Page 50: Glossary

    GLOSSARY GLOSSARY Cosine Response The cosine error for the external sensor for typical applications is <1%. External Sensor An external PAR sensor allows the LP-80 to make simultaneous above- and below-canopy PAR measurements. This makes multiple PAR measurements under the canopy in variable light conditions without having to keep moving the instrument in and out of the canopy to update the above canopy PAR reference.
  • Page 51 LP-80 Table 3 Typical χ Values Crop Crop χ χ Ryegrass 0.67 Rape 1.92–2.13 Maize 0.76 Cucumber 2.17 0.80–1.27 Tobacco 1.29–2.22 Wheat 0.96 Potato 1.70–2.47 Barley 1.20 Horse bean 1.81–2.17 Timothy 1.13 Sunflower 1.81–2.31 Sorghum 1.43 White clover 2.47–3.26 Lucerne 1.54 Strawberry 3.03...
  • Page 52 GLOSSARY calculated by the LP-80 based on the global position and the time 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 0°...

  • Page 53: Index

    INDEX INDEX fractional beam radiation (Fb) 5, 46 battery icon 39 replacement 39–41 leaf area index (LAI) 4, 5, 20, 46 type 1, 15 leaf distribution parameter (χ) 5, 29, 46–47 LP-80 Utility Actions menu 23 cable 1, 15, 16 download data 11–12 calibration 37–39 Edit Menu 22–23...
  • Page 54 INDEX About 22 Active Segments 21 Annotate 9 Calibration 20 Configuration 2, 19–22 contrast 21 Data 10, 19 Date 3, 20 Detailed Data 10 External Sensor Constant 20 Leaf Distribution 20 Location 3, 20 Log 8, 18–19 PAR 4, 18 Save Method 9 Time 4, 20 View Data 10...
  • Page 55 10888-02 2.28.2020 METER Group, Inc. USA 2365 NE Hopkins Court 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...

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