LI-COR LI-250A User manual

Instruction
Manual
LI-250A
LI-250A
Light Meter
Light Meter
®
LI-COR, inc. ●Environmental
4421 Superior Street ●P.O. Box 4425 ●Lincoln, Nebraska 68504
Phone: [phone] ● FAX: [phone]
Toll-free 1-800-447-3576 (U.S. & Canada)
[e-mail]
www.licor.com
®

CE Marking
The LI-250A is a CE-marked product. For conformity
information, contact LI-COR Support at
http://www.licor.com/envsupport. Outside of the U.S.,
contact your local sales office or distributor.
Doc. #53-16006-A
June 30, 2016
LI-1500/LI-1500G Light Sensor Logger/LI-250A Light Meter
Part Name Toxic and Hazardous Substances or Elements
(Pb) (Hg) (Cd) (Cr(VI)) (PBB) (PBDE)
PCBs)
X O O O O O
Cables and Wires)
X O O O O O
(Metal Parts)
X O O O O O
(
Plastic Parts)
O O O O O O
(
Batteries)
O O O O O O
SJ/T 11364
O = GB/T 26572
(indicates that the content of the toxic and hazardous substance in all the Homogeneous
Materials of the part is below the concentration limit requirement as described in
GB/T 26572 ).
X = GB/T 26572
(indicates that the content of the toxic and hazardous substance in at least one Homogeneous
Material of the part exceeds the concentration limit requirement as described in
GB/T 26572 ).
LI-1500/LI-1500G / LI-250A

LI-250A
Light Meter
Instruction Manual
Publication Number 984-07507
March, 2004
®
LI-COR, Inc.
Environmental
4421 Superior Street
P.O. Box 4425
Lincoln, Nebraska 68504
Phone: [phone]
FAX: [phone]
Toll-free 1-800-447-3576 (U.S. & Canada)
[email protected]
www.licor.com

ii
How to Use this Manual
This manual contains operation and maintenance infor-
mation for the LI-250A Light Meter. Read the operating
instructions before using the LI-250A.
NOTICE
The information contained in this document is subject to change
without notice.
LI-COR MAKES NO WARRANTY OF ANY KIND WITH
REGARD TO THIS MATERIAL, INCLUDING, BUT NOT
LIMITED TO THE IMPLIED WARRANTIES OF MER-
CHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE. LI-COR shall not be liable for errors contained herein
or for incidental or consequential damages in connection with the
furnishing, performance, or use of this material.
This document contains proprietary information which is protected
by copyright. All rights are reserved. No part of this document
may be photocopied, reproduced, or translated to another language
without prior written consent of LI-COR, inc.
Copyright 2004, LI-COR, inc.
1st Printing - March, 2004

iii
Table of Contents
Section 1. Operation Summary
1.1 Configuration vs. Measurement Mode..................... 5
1.2 Making Measurements ............................................. 5
Section 2. Sensors & Accessories
2.1 Compatible Sensors ................................................. 9
2.2 Sensor Calibration.................................................... 10
2.3 Accessories .............................................................. 13
2.4 Power Requirements ................................................ 13
APPENDIX A. Specifications
APPENDIX B. Conversion Table

5
1Operation Summary
Read this section to configure and operate the LI-250A.
Note that abbreviated programming instructions can also be
found on the LI-250A back panel.
1.1 Configuration vs. Measurement
Mode
The LI-250A has two modes of operation; Configuration
and Measurement mode. In configuration mode, you can
enter calibration multipliers for two different light sensors,
or enter two multipliers for the same sensor. For example,
you might enter a multiplier that applies to measurements
under water and one that applies to measurements in air for
an LI-192SA Underwater Quantum Sensor. In measure-
ment mode the LI-250A makes continuous measurements
until either the HOLD key or the CAL key is pressed.
1.2 Making Measurements
The LI-250A utilizes a 5-key keypad; note that many of the
keys have two functions. The active function depends on
whether the LI-250A is in Measurement or Configuration
mode. In measurement mode, the keys perform the
function shown in green; in configuration mode, the keys
perform the function shown in white.

Operation Summary
6
1. Attach the desired sensor.
2. Press and hold the ON key for about 2 seconds, and
then release to turn the instrument on. You will be in
measurement mode.
3Press CAL to enter configuration mode, where you can
display or change the calibration multiplier currently
in use. The display will show CAL.
4. Press UNITS until the units label on the display
matches the sensor type. Readings will be incorrect if
the Units Label does not match the sensor type.
Sensor Type Units Label Readout Units
Quantum
Pyranometer
Photometric
µmol
W m-2
lux or Klux
µmol s-1 m-2
Watts m-2
lux or Kilolux
5. Press the ↑or ↓keys to change the displayed
multiplier value. Press and hold the arrow keys down
to scroll the values rapidly.
Important Note: Measurement units must
match the sensor type; no unit conversions are
performed.
6. Press CAL again to store the displayed multiplier value
and units label and use them to take measurements; or
7. Press MULT SELECT if you wish to display the second
multiplier. NOTE: Pressing MULT SELECT before

Operation Summary
7
pressing CAL (step 6) discards any changes you have
made to the multiplier currently shown on the display.
8. Edit the second multiplier following steps 5-7 above.
9. Press CAL again to store the displayed multiplier value
and units label and use them to take measurements.
Note that pressing CAL when in measurement mode will
display the multiplier in current use. The multiplier dis-
played when CAL is pressed again will be stored as the
active multiplier, whether you have changed it or not.
While in measurement mode, you can press HOLD to retain
the current reading on the display, until the HOLD key is
pressed again.
Press AVG to perform a 15 second average, which will be
displayed in Hold mode. Press the HOLD key to resume
measurements.
Press the OFF key to turn the power off. The LI-250A will
automatically shut off after 25 minutes of inactivity in
measurement mode.

Operation Summary
8
Precaution
The LI-250A is environmentally sealed. However, please
use appropriate precautions to protect the meter from
immersion or prolonged contact with water, especially in
marine environments. Water damage is not covered under
the LI-250A warranty.

9
2 Sensors & Accessories
2.1 Compatible Sensors
The LI-250A is compatible with all LI-COR type 'SA'
radiation sensors. It is important that the LI-250A be
properly configured for the specific sensor used. A
quantum sensor must be used to make measurements of
photosynthetically active radiation (µmol s-1 m-2 of PAR),
a pyranometer for measurements of solar radiation (W m-2),
and a photometric sensor for measurements of illuminance
(lux). For example, it is not possible for a pyranometer to
read out in units of lux. If you want to configure the LI-
250A to read out in lux, you must use the photometric
sensor.
LI-COR type 'SB' radiation sensors are also compatible if
the Calconnector (Calibration connector) is detached from
the BNC connector.
LI-COR type 'SZ' radiation sensors are not compatible with
the LI-250A; they may, however, be fitted with a BNC con-
nector. Contact LI-COR for further information.
Recalibration of all LI-COR radiation sensors is rec-
ommended every two years.
Complete information concerning the sensors that can be
used with the LI-250A is found in the type 'SA' LI-COR
Radiation Sensors instruction manuals. In addition, several
technical reports on LI-COR sensors are available. These
include a report entitled "Radiation Measurements", which

Sensors & Accessories
10
summarizes the types of measurements that can be made
with each LI-COR sensor and contains conversion factors
for commonly used measurement units. A report concern-
ing the immersion effect and cosine collecting properties of
underwater sensors is also available (Roemer, Hoagland
report. Request Application Note #110).
2.2 Sensor Calibration
All LI-COR radiation sensors produce a current pro-
portional to the radiation intensity. During factory cali-
bration, sensor output (in microamps) is measured while the
sensor is exposed to a standard lamp of known intensity.
The sensor output at this intensity has general units of
microamps per radiation unit and is called the Calibration
Constant (Calconstant). Each sensor has a slightly differ-
ent output at a given radiation intensity and will therefore
have a unique Calconstant.
The LI-250A measures the current output of the sensor in
units of microamps, and converts the measured current to
units of radiation. To make this conversion, the LI-250A
uses the sensor Calibration Multiplier. The Calibration
Multiplier is the negative reciprocal of the Calconstant.
Multiplier Calcons t =−1
tan
The Calibration Multiplier is always a negative number,
and is expressed in radiation units per microamp. The
LI-250A multiplies the current reading in microamps by the
multiplier.

Sensors & Accessories
11
Since the Calibration Multiplier is unique for each sensor, it
must be entered into the LI-250A each time the sensor is
changed or recalibrated.
NOTE: Always enter the Calibration Multiplier, not
the Calconstant. If the Calconstant is entered any data
collected will be erroneous.
For type 'SA' sensors purchased after September, 1985, the
calibration multiplier is given on the certificate of calibra-
tion, and is also attached to the sensor. An example of a
calibration label attached to a quantum sensor appears
below, which would contain the value of the multiplier, as
well as the serial number of the sensor, and the date of its
most recent calibration.
NOTE: Tcoff is a time coefficient that is used to convert
integrated data to the proper units when using the LI-1000
Datalogger to log data with certain sensors. This value can
be ignored when using the LI-250A.
MULT: XXX.XX
tcoff: 0.0036
Units: µmol s-1 m-2 per µA
SERIAL NO.
CAL DATE: DD/MM/YR
®
For the LI-192SA and LI-193SA Underwater Quantum
Sensors there are two calibration multipliers; one for "in

Sensors & Accessories
12
air" operation and one for "in water" operation. Use the
multiplier that is appropriate for your application.
If the calibration constant for your sensor has been lost or
misplaced, it can be obtained from LI-COR by providing
the serial number of the sensor.
Converting Calconstants to Multipliers
For LI-COR sensors that are not type 'SA' (i.e., type 'SB',
etc.), the calibration multiplier must be calculated from the
calibration constant given on the certificate of calibration.
EXAMPLE: Calculate the multiplier for an LI-190SB
Quantum sensor with a calibration constant of 8.0
µAmps/1000 µmol s-1 m-2.
Multiplier =−
( )
µ
( )
µ
1 1000
8
s m
Amps
-1 -2
mol
=−µ
µ
125 0
1
. mol s m
Amp
-1 -2

Sensors & Accessories
13
2.3 Accessories
The following accessories and sensors are available for the
LI-250A. Contact LI-COR for current information.
250-01 Carrying Case - A soft-sided case for the LI-250A
and terrestrial type radiation sensors. Size: 20.3 cm L ×
10.2 cm W × 9 cm D (8" ×4" ×3.5"). Weight: 98 g (0.216
lbs).
LI-COR Radiation Sensors: Type 'SA' (e.g. LI-190SA)
with BNC connectors.
LI-190SA Quantum Sensor - measures Photosynthetically
Active Radiation (PAR) in natural sunlight, under plant
canopies, and in growth chambers and greenhouses.
LI-191SA Line Quantum Sensor - averages PPFD over its
one meter length for plant canopy PPFD profile studies.
LI-192SA Underwater Quantum Sensor* - measures
Photosynthetic Photon Flux Density (PPFD) in air or under
water incident on a flat plane.
LI-193SA Spherical Quantum Sensor* - measures photon
flux from all directions under water. This measurement is
called Photosynthetic Photon Flux Fluence Rate (PPFFR).
LI-200SA Pyranometer Sensor - measures global solar
radiation (sun plus sky) and provides a typical accuracy of
±5% under unobstructed daylight conditions.
LI-210SA Photometric Sensor - measures visible radiation
and has a spectral response equal to that for the average
human eye. Readout of illuminance (in lux) is used for
lighting studies or architectural modeling.
* Requires 2222UWB cable.

Sensors & Accessories
14
2003S Mounting and Leveling Fixture - The 2003S is for
use with all LI-COR terrestrial type sensors.
2222SB Extension Cable - For use with all LI-COR ter-
restrial type sensors. Available in 15.2 m (50 ft), 30.4 m
(100 ft), or custom lengths to 304 m (1000 ft).
216 Replacement Battery - 9 Volt transistor type. The
LI-250A requires one for replacement.
2.4 Power Requirements
Power is supplied by one 9 volt transistor battery.
Eveready alkaline #522 (LI-COR part #442-15962) or
equivalent may be used. Battery life is in excess of 150
hours. A LO BAT message is displayed when there is less
than 20 hours of battery life remaining. The battery should
be replaced immediately after the LO BAT message is
displayed to ensure reliable operation.
The battery compartment is accessed through a screw-
retained panel on the back of the instrument case. Remove
the battery by lifting on the end of the battery with the
terminals. Insert the new battery by pushing straight down
on the battery; do not try to insert at an angle.
Although typical battery life is more than 150 hours of
continuous operation, it is dependent upon the storage tem-
perature. Do not store the LI-250A at high temperatures.

A-1
Appendix A. Specifications
Accuracy: 25 °C: Typically ± 0.4% of reading [± 3 counts
on the least significant digit displayed (all ranges)].
0-55 °C: Typically ± 0.6% of reading [± 3 counts on the
least significant digit displayed (all ranges)].
Range Selection: Autoranging (3 ranges).
Sensor Calibration: Calibration multipliers for two
sensors are stored in memory. Calibration multipliers are
entered from the keypad.
Sensor Averaging: Sensor output is averaged for 15
seconds when AVG key is pressed in Measurement mode.
Averages are displayed in HOLD mode to retain the
average on the display.
Linearity: ±0.05%.
Operating Conditions: 0 to 55 °C, 0 to 95% RH (non-
condensing).
Storage Conditions: -55 to 60 °C, 0 to 95% RH
(non-condensing).
Display: 4 1/2 digit custom LCD display. Updated every
0.5 seconds.
Keypad: Sealed, 5-key tactile response keypad.
Battery Life: 150 hours typical with continuous operation.
Automatic shutoff after 25 minutes of inactivity in
measurement mode.
Power Requirement: One 9V Eveready Alkaline #522 or
equivalent.

Specifications
A-2
Low Battery Detection: Low battery indicator displayed
with approximately 20 hours battery life remaining.
Size: 15 L ×8.2 W ×3.3 cm D (5.9" ×3.2" ×1.3").
Weight: 0.26 kg (0.57 lbs).
Sensors: Any LI-COR sensor with BNC connector;
Quantum, Pyranometer, or Photometric.
Warranty: 1 year parts and labor.
LI-250A Range and Resolution:
Sensor Type
Quantum
Radiometric
Photometric
Range Resolution
0-199 µmol s-1 m-2
-1999
-19999
0-19 W m-2
-199
-1999
0-1999 lux
-19999 lux
0-199 klux
0-199 fc
-1999
-19999
0.01 µmol s-1 m-2
0.1
1
0.001 W m-2
0.01
0.1
0.1 lux
1 lux
0.01 klux
0.01 fc
0.1
1

B-1
Appendix B. Conversion Table
Type of
Measurement
Instantaneous Measurements
Quantum 1.0 µm s-1 m-2 = 1 µEs-1 m-2
= 6.022 •1017 photons s-1m-2
= 6.022 •1017 quanta s-1 m-2
= 6.022 •1013 quanta s-1 cm-2
Radiometric 1 W m-2 = 1.433 •10-3 cal cm-2 min-1
= 1.433 •10-3 langley min-1
= 0.100 mW cm-2
= 100 µW cm-2
= 1.0 J s-1 m-2
= 1000 erg s-1 cm-2
= 0.317 BTU ft-2 h-1
= 5.283 •10-3 BTU ft-2 min-1
Photometric 1 lux = 1 lm m-2
= 0.0929 lm ft-2
= 0.0929 fc
= 0.001 klux

Warranty
Each LI-COR, inc. instrument is warranted by LI-COR, inc. to be
free from defects in material and workmanship; however,
LI-COR, inc.'s sole obligation under this warranty shall be to repair
or replace any part of the instrument which LI-COR, inc.'s
examination discloses to have been defective in material or
workmanship without charge and only under the following
conditions, which are:
1. The defects are called to the attention of LI-COR, inc. in
Lincoln, Nebraska, in writing within one year after the shipping
date of the instrument.
2. The instrument has not been maintained, repaired, or altered by
anyone who was not approved by LI-COR, inc.
3. The instrument was used in the normal, proper, and ordinary
manner and has not been abused, altered, misused, neglected,
involved in and accident or damaged by act of God or other
casualty.
4. The purchaser, whether it is a DISTRIBUTOR or direct
customer of LI-COR or a DISTRIBUTOR'S customer, packs and
ships or delivers the instrument to LI-COR, inc. at LI-COR inc.'s
factory in Lincoln, Nebraska, U.S.A. within 30 days after
LI-COR, inc. has received written notice of the defect. Unless
other arrangements have been made in writing, transportation to
LI-COR, inc. (by air unless otherwise authorized by LI-COR, inc.)
is at customer expense.
5. No-charge repair parts may be sent at LI-COR, inc.'s sole
discretion to the purchaser for installation by purchaser.
6. LI-COR, inc.'s liability is limited to repair or replace any part of
the instrument without charge if LI-COR, inc.'s examination