Decagon Devices AccuPAR LP-80 User manual

AccuPAR PAR/LAI
Ceptometer
Model LP-80
Operator’s Manual
Decagon Devices, Inc.
Version: December 13, 2013 — 08:29:36

AccuPAR LP-80
Decagon Devices, Inc.
2365 NE Hopkins Court
Pullman WA 99163
Phone: [phone]
Fax: [phone]
Website: www.decagon.com
Email: supp[email protected] or [email protected]
Trademarks
AccuPAR and Ceptometer are registered trademarks of
Decagon Devices, Inc. c 2006-2013
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AccuPAR LP-80 CONTENTS
Contents
1 Introduction 1
1.1 Customer Support . . . . . . . . . . . . . . . . . . . . 1
1.2 About This Manual . . . . . . . . . . . . . . . . . . . 1
1.3 Warranty ......................... 2
1.4 Seller’s Liability . . . . . . . . . . . . . . . . . . . . . . 2
2 About the LP-80 3
2.1 AccuPAR LP-80 Instrument Specifications . . . . . . . 3
2.2 Overview of the LP-80 . . . . . . . . . . . . . . . . . . 4
2.3 Components of the LP-80 System . . . . . . . . . . . . 4
2.4 Turning on the instrument . . . . . . . . . . . . . . . . 6
3 Definitions 8
4 PAR/LAI Menu 12
4.1 Taking Measurements . . . . . . . . . . . . . . . . . . 12
4.2 Saving and Annotating Readings . . . . . . . . . . . . 14
5 Log Menu 15
6 Data Menu 17
6.1 View............................ 17
6.2 Download ......................... 18
6.3 Description of Outputs . . . . . . . . . . . . . . . . . . 20
6.4 Erase............................ 22
7 LP-80 Utility Software 23
7.1 Downloading Data . . . . . . . . . . . . . . . . . . . . 23
7.1.1 Data File Formats . . . . . . . . . . . . . . . . 23
7.1.2 Data Organization . . . . . . . . . . . . . . . . 24
7.2 ErasingData ....................... 25
7.3 Setting the Date and Time . . . . . . . . . . . . . . . 26
7.4 Viewing LP-80 Information . . . . . . . . . . . . . . . 26
7.5 The Preferences Menu . . . . . . . . . . . . . . . . . . 27
7.5.1 Data File Tab . . . . . . . . . . . . . . . . . . . 27
7.6 Communications Tab . . . . . . . . . . . . . . . . . . . 28
7.7 Application Tab . . . . . . . . . . . . . . . . . . . . . 28
7.8 Software and Firmware Updates . . . . . . . . . . . . 29
iii

CONTENTS AccuPAR LP-80
8 Config Menu 30
8.1 Calibration ........................ 31
8.1.1 Location...................... 32
8.1.2 Date and Time . . . . . . . . . . . . . . . . . . 33
9 PAR and LAI Theory 37
9.1 PAR (Photosynthetically Active Radiation) . . . . . . 37
9.2 Average and Intercepted PAR . . . . . . . . . . . . . . 37
9.3 Using PAR to determine Leaf Area Index . . . . . . . 40
9.4 Applications and Examples . . . . . . . . . . . . . . . 42
9.5 Extinction Coefficient and Canopy Structure . . . . . 42
9.5.1 Correction of PAR for Sun Angle . . . . . . . . 45
9.6 LAI measurements & Non-Random Distribution . . . 47
9.7 Zenith Angle and Equation of Time . . . . . . . . . . 49
10 Measurement Tips 53
10.1 Above Canopy (External) Sensor . . . . . . . . . . . . 53
10.2SampleSize........................ 53
10.3 Clumping in Canopies . . . . . . . . . . . . . . . . . . 54
10.4 LAI Sampling in Row Crops . . . . . . . . . . . . . . . 54
11 Care and Maintenance 56
11.1Batteries.......................... 56
11.2 Cleaning the Probe and Controller . . . . . . . . . . . 56
11.3 Recalibration . . . . . . . . . . . . . . . . . . . . . . . 57
11.4 General Precautions . . . . . . . . . . . . . . . . . . . 57
12 Troubleshooting 58
13 Support and Repair 67
13.1RepairCosts ....................... 68
14 Further Readings 69
15 Declaration of Conformity 74
16 Appendix A 75
16.1 External Sensor Information . . . . . . . . . . . . . . . 75
16.2 Spectral Response . . . . . . . . . . . . . . . . . . . . 75
iv

AccuPAR LP-80 1 INTRODUCTION
1 Introduction
Welcome to Decagon’s AccuPAR model LP-80 PAR/LAI Ceptome-
ter. The AccuPAR measures Photosynthetically Active Radiation
(PAR) and can invert these readings to give Leaf Area Index (LAI)
for your plant canopy. This manual is designed to help you accom-
plish your research goals, and understand how to get the most out
of your AccuPAR.
1.1 Customer Support
If you ever need assistance with your AccuPAR or have any questions
or feedback, there are several ways to contact us. Decagon has Cus-
tomer Service Representatives available to speak with you Monday
through Friday, between 7am and 5pm Pacific time.
Note: If you purchased your AccuPAR LP-80 through a distribu-
tor, please contact them for assistance.
Email:
supp[email protected] or [email protected]
Phone:
509-332-5600
Fax:
509-332-5158
If contacting us by email or fax, please include as part of your message
your instrument serial number, your name, address, phone number,
fax number, and a description of your problem or question.
1.2 About This Manual
This manual includes instructions for setting up your AccuPAR LP-
80, verifying the calibration of the instrument, preparing samples,
and maintaining and caring for your instrument. Please read these
1

1 INTRODUCTION AccuPAR LP-80
instructions before operating the LP-80 to ensure that the instrument
performs to its full potential.
1.3 Warranty
The AccuPAR has a one year warranty on parts and labor. Your
warranty is automatically validated upon receipt of the instrument.
1.4 Seller’s Liability
Seller warrants new equipment of its own manufacture against defec-
tive workmanship and materials for a period of three years from the
date of receipt of equipment.
Note: We do not consider the results of ordinary wear and tear,
neglect, misuse, accident and excessive deterioration due to corro-
sion from any cause as defects.
The Seller’s liability for defective parts shall in no event exceed the
furnishing of replacement parts Freight On Board the factory where
originally manufactured. Material and equipment covered hereby
which is not manufactured by Seller shall be covered only by the
warranty of its manufacturer. Seller shall not be liable to Buyer for
loss, damage or injuries to persons (including death), or to property
or things of whatsoever kind (including, but not without limitation,
loss of anticipated profits), occasioned by or arising out of the instal-
lation, operation, use, misuse, nonuse, repair, or replacement of said
material and equipment, or out of the use of any method or process
for which the same may be employed. The use of this equipment
constitutes the buyer’s acceptance of the terms set forth in this war-
ranty. There are no understandings, representations, or warranties
of any kind, express, implied, statutory or otherwise (including, but
without limitation, the implied warranties of merchantability and
fitness for a particular purpose), not expressly set forth herein.
2

AccuPAR LP-80 2 ABOUT THE LP-80
2 About the LP-80
The AccuPAR model LP-80 is a menu-driven, battery-operated lin-
ear 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. The probe
contains 80 independent sensors, spaced 1 cm apart. The photosen-
sors measure PAR (Photosynthetically Active Radiation) in the 400
to 700 nm waveband. The AccuPAR displays PAR in units of micro-
mols per meter squared per second (µmol m−2s−1). The instrument
is capable of hand-held or unattended measurement.
2.1 AccuPAR LP-80 Instrument Specifications
Operating Environment:
0◦to 50◦C (32◦−122◦F)
0 to 100% relative humidity
Probe Length: 86.5 cm
Number of Sensors: 80
Overall Length: 102 cm (40.25 in)
Probe Cross-Section: 19 cm x 9.5 cm (.75 x .375 in)
Micro Controller Dimensions: 15.8 x 9.5 x 3.3 cm (6.2 x 3.75 x 1.3
in)
PAR Range: 0 to 2,500 µmol m−2s−1
Resolution: 1 µmol m−2s−1
Minimum Spatial Resolution: 1 cm
Data Storage Capacity: 1 MB Flash
Unattended Logging Interval: User selectable, between 1 and 60
min
Instrument Weight (w/ Batteries): 0.55 kg (1.21 lbs)
Data Retrieval: direct via RS-232
3

2 ABOUT THE LP-80 AccuPAR LP-80
Keypad: 7-Key menu-driven
Clock: 24-hour ±1 minute per month
Interface Cable: RS-232 cable
Power: Four AAA Alkaline cells.
External PAR Sensor Connector: Locking 5-pin sealed circular con-
nector
2.2 Overview of the LP-80
Decagon designed the menu-driven LP-80 interface for ease of use.
There are four menus to choose from: the PAR/LAI menu, Log menu,
Data menu, and Config menu. You navigate between the menus by
pressing the MENU button, and select items within each menu using
the up and down arrow keys, and the ENTER or ESC keys.
The AccuPAR can be operated in environments with temperatures
from 0 to 50◦C, and in relative humidities of up to 100%. The instru-
ment ships with an RS-232 interface cable to allow for downloading
data to a computer, an external PAR sensor to allow for calibration,
and simultaneous above and below canopy PAR measurements. The
AccuPAR operates on four AAA alkaline batteries.
2.3 Components of the LP-80 System
The AccuPAR and its accessories arrive in a durable foam-padded
carrying case. Your shipment should arrive with the following items.
•AccuPAR model LP-80
•RS-232 Cable
•Operator’s Manual
•External PAR Sensor
•#1 Phillips Screwdriver
4

AccuPAR LP-80 2 ABOUT THE LP-80
Figure 1: Product Features
Figure 2: LP-80 Keypad
5

2 ABOUT THE LP-80 AccuPAR LP-80
The LP-80 keypad is a 7-key panel, designed for ease of use and
intuitive navigability through the operating system. Here is a brief
description of the key functions, refer to Figure 2 for Keypad de-
scriptions.
ON/OFF Key: Located in the upper left corner, it turns the
instrument on or off. The AccuPAR will turn itself off auto-
matically after 10 minutes of inactivity.
MENU Key: Cycles between the four menus.
UP and DOWN ARROW KEYS: In PAR Sampling menu,
they initiate above (up arrow) and below (down arrow) canopy
PAR readings. In other menus, they are used to navigate to
items within those menus and to change numeric values in sub
menus.
Round Green Key: The circular key in the upper right corner
of the keypad (by the AccuPAR logo) also serves the same
function as the Down-arrow key. It is designed as an ergonomic
alternative when taking multiple below-canopy PAR samples
ESC: Cancels the current PAR reading displayed in the lower half
of the PAR sampling menu, cancels out of menu options, and
navigates to the left in the annotation screen.
ENTER: Saves the current PAR readings in the PAR sampling
menu, selects items in other menus, and navigates to the right
in the annotation screen.
2.4 Turning on the instrument
When you first turn on the instrument, it will be in the PAR sampling
menu, in which you will see real-time PAR data displayed in the
center portion of the screen. If you have the external PAR sensor
connected, you will also see its real-time PAR data.
6

AccuPAR LP-80 2 ABOUT THE LP-80
Figure 3: PAR Data Return Screenshot
At any time, you can cycle between the four menus by pressing the
MENU key. The menus are indicated by the tabs on the top of the
screen, with the active menu in the foreground. If the battery is
low, a low battery indicator will appear to the right of the menu
tabs. Later chapters discuss each menu in detail and how to use the
features that each provides.
7

3 DEFINITIONS AccuPAR LP-80
3 Definitions
The AccuPAR LP-80 uses several variables to calculate Leaf Area
Index, and displays values for these variables on the screen as mea-
surements are taken. This chapter will discuss these variables and
their definitions. If you are not familiar with them, we recommend
that you review this chapter before proceeding with measurements.
PAR
PAR (photosynthetically active radiation) is the radiation in the 400
to 700 nanometer waveband. It represents the portion of the spec-
trum which plants use for photosynthesis. Under a plant canopy,
radiation levels can vary from full sun to almost zero over the space
of a few centimeters. Therefore, reliable measurement of PAR re-
quires many samples at different locations under the canopy.
The AccuPAR measures PAR either manually or in unattended log-
ging mode. Intercepted PAR data can be used for determining im-
portant parameters of canopy structure and for the calculation of
LAI. An external point sensor may be used to collect instantaneous
above canopy PAR measurements when sampling under or within a
canopy. You also have the option of segmenting the probe to reflect
spatial changes in the plant canopy. This is useful when evaluating
discontinuous and irregular canopies, or to limit the number of active
sensors along the probe.
Tau (τ)
Tau is another variable in the LAI inversion equations. It is de-
fined as the ratio of below canopy PAR measurements to the most
recent above canopy PAR value. It is measured automatically by the
instrument, based upon the PAR readings you make. The current τ
value is displayed and updated in the lower left corner of the screen
in the PAR menu. Chapter 9 provides further explanation of the
significance of Tau.
8

AccuPAR LP-80 3 DEFINITIONS
LAI(L)
LAI (Leaf Area Index) is defined as the area of leaves per unit area
of soil surface. It is a valuable measurement in helping to assess
canopy density and biomass. The AccuPAR 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 measure-
ment value, and a leaf area distribution parameter (also known as χ)
for your particular canopy. The AccuPAR automatically calculates
both the zenith angle and fractional beam reading, and requires you
to input a value for χin the setup menu.
External Sensor
An external PAR sensor is provided with the AccuPAR to allow
you to make simultaneous above and below canopy PAR measure-
ments. This is useful if you want to be able to make 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. The external sensor is also
the PAR standard to which the wand is calibrated.
Zenith Angle (z)
Zenith angle can be defined as the angle the sun makes with respect
to the zenith, or the point in the sky directly overhead, vertical to
where you stand. The zenith is defined as being 0◦and the horizon
is 90◦. The zenith angle of the sun is necessary for calculation of
certain canopy structure parameters, such as LAI. It is calculated by
the AccuPAR based on your global position and the time of day, and
is displayed in the lower right corner of the screen when taking above
and below PAR measurements. To make sure this value is accurate,
you must first correctly set the longitude, latitude, date, and time of
day in the setup menu.
Fraction of Beam Radiation (Fb)
9

3 DEFINITIONS AccuPAR LP-80
Fractional beam radiation is the ratio of direct beam radiation com-
ing from the sun to radiation coming from all ambient sources like the
atmosphere or reflected from other surfaces. A fractional beam radi-
ation value is necessary for calculation of LAI using PAR data. The
AccuPAR obtains this value by comparing the above canopy PAR
measurement to the calculated value of potential incoming solar radi-
ation at your location and zenith angle. The current calculated Fbis
displayed and updated at the bottom of the screen in the PAR menu.
Leaf Distribution Parameter (χ)
Leaf Distribution Parameter (also known as chi, or χ) refers to the
distribution of leaf angles within a canopy. The parameter χis the
ratio of the length of the horizontal to the vertical axis of the spheroid
described by the leaf angle distribution of a canopy. It can also be
measured as the ratio of the projected area of an average canopy
element (a leaf, for example) on a horizontal plane to its projection
on a vertical plane. The default value for χis 1.0, which assumes the
canopy angle distribution to be spherical. Onions are a good exam-
ple of a strongly vertical crop. For onions, χwould be about 0.7. On
the other extreme, strawberries, a crop with a strongly horizontal
nature, would have a χvalue of about 3.
Table 1 gives some typical values for χ. In some cases a range of
values is given, indicating the variability that is to be expected for
χin any canopy. Fortunately, the value of LAI computed is not
strongly dependent on the value of χchosen. The AccuPAR uses a
value of χ=1.0 as its default.
10

AccuPAR LP-80 3 DEFINITIONS
Table 1: Typical χValues
Crop χCrop χ
Ryegrass 0.67 to 2.47 Rape 1.92 to 2.13
Maize 0.76 to 2.52 Cucumber 2.17
Rye 0.80 to 1.27 Tobacco 1.29 to 2.22
Wheat 0.96 Potato 1.70 to 2.47
Barley 1.20 Horse Bean 1.81 to 2.17
Timothy 1.13 Sunflower 1.81 to 2.31
Sorghum 1.43 White Clover 2.47 to 3.26
Lucerne 1.54 Strawberry 3.03
Hybrid Swede 1.29 to 1.81 Jerusalem Artichoke 2.16
Sugar Beet 1.46 to 1.88
11

4 PAR/LAI MENU AccuPAR LP-80
4 PAR/LAI Menu
The first menu option is the PAR/LAI sampling menu, which is used
for measurements with the AccuPAR. The default screen is similar
to the PAR screen.
This PAR screen indicates that the current real-time PAR level is
2µmols/m2s (this example was taken indoors) 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 will be also displayed above the real-time light bar PAR data.
4.1 Taking Measurements
To make an above-canopy PAR measurement, press the up-arrow
key in this menu. The resulting value will be displayed in the upper
right section of the screen. To make measurements below the canopy,
press the down-arrow key or the green circular key in the upper right
corner of the keypad. You must plug in a external sensor or take an
above canopy PAR reading first before summary data will update.
The LP-80 recalculates summary data after each below canopy PAR
reading. Other relevant data displays at the bottom of the screen.
12

AccuPAR LP-80 4 PAR/LAI MENU
LP-80 updates and displays the current calculated Tau (τ), LAI
value, beam fraction (Fb), leaf distribution parameter (χ) and zenith
angle (z) values are updated and displayed at the bottom of the
screen with each subsequent below canopy PAR measurement. If
the external sensor is attached and you press an up or down arrow,
the LP-80 records both above and below canopy readings.
Pressing ENTER brings up the Save screen which allows you to save
as is, annotate, or discard. Pressing ESC discards the values. Both
options clear the screen for new data. The values displayed at the
bottom of the screen are dependent on how you have set up your
instrument in the Setup menu. Please refer to chapter 3 Definitions
or chapter 8 Theory for a more detailed description of these variables
and their definitions.
With each above or below canopy measurement, a number appears
to the right of the PAR value that indicates the number of completed
measurements. The displayed PAR value reflects the sample average.
The LP-80 made four above and three below canopy measurements in
the previous PAR screen shot. Therefore, in the above sample screen,
four above and three below canopy measurements have been made,
so the average of the four above-canopy PAR values is 211 µmols,
while the average of the three below-canopy values is 20 µmols.
Note: When you connect the external sensor, the LP-80 uses read-
ings from the external sensor as above PAR readings to calculate LAI.
Summary data on the bottom of the screen are recalculated using the
last above canopy reading with each subsequent below canopy reading.
13

4 PAR/LAI MENU AccuPAR LP-80
4.2 Saving and Annotating Readings
To save a reading once you are done taking above and below PAR
data, press ENTER. The Save Method screen appears.
You have three options at the Save Method screen.
1. Select “Save” and press ENTER to save your information.
Data will be stored with the time and date you take the mea-
surement.
2. Select “Discard” and press ENTER to return to the main screen
and start over with a new reading.
3. Select “Annotate” and press ENTER to give your data a file
name or description, e.g. “Plot 1.” Selecting “Annotate” will
cause the Annotate screen to appear.
You will see a series of lines, with a set of arrows above and below
the first, in the Annotate screen. If you have annotated a previous
reading, the old annotation will remain to be changed or deleted.
Use the arrow keys to select a letter or number and press ENTER to
move to the next character. When you finish, keep pressing ENTER
until the screen returns to the PAR menu.
14

AccuPAR LP-80 5 LOG MENU
5 Log Menu
When you advance to the LOG menu, the Log screen appears.
The Log menu allows you to put the instrument in an unattended
PAR data logging mode. In this mode, the AccuPAR will automat-
ically measure and store PAR data at an interval that you specify.
Note: LAI and Tau are calculated more accurately by manually sam-
pling PAR beneath a canopy at random locations, instead of leaving
the LP-80 in one place and collecting data in log mode.
You can select the measurement interval by pressing the up or down
arrows. This will allow you to select any value between 1 and 60
minutes. In the previous Log screen shot, the LP-80 is set to make
and store a measurement every one minute. To activate the logging
mode, press the ENTER button. To cancel the logging mode press
Escape. When you enable the logging mode, the screen will begin to
return data.
The LP-80 will store data taken in this mode automatically without
annotation to memory.
15

5 LOG MENU AccuPAR LP-80
Note: You can move from this menu to other menus while the logging
mode is activated. While activated, the LP-80 continues to log data
whether or not the AccuPAR display is on or if you are in a different
menu.
Caution: This mode is for short-term experiments (one or
two days). We did not design the LP-80 to be left in the
field for long periods of time as damage from moisture may
occur.
16