LI-COR LI-250A User manual

LI-250A Light Meter
Instruction Manual

LI-250A Light Meter
Instruction Manual
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Notice
This manual contains operation and maintenance inform-
ation for the LI-250A Light Meter. Read the operating
instructions before using the LI-250A.
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
MERCHANTABILITY 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 trans-
lated to another language without prior written consent of
LI-COR, Inc.
Copyright © 2004-2019, LI-COR, Inc. All rights reserved.
Document number: 984-07507
1st Printing - March 2004
Updated: Wednesday, July 24, 2019
ii

Contents
Section 1. Operation summary
Configuration mode vs. measurement mode 1
Making measurements 2
Power requirements 4
Section 2. Overview of compatible sensors
Overview of radiation sensor calibration 5
Understanding the certificate of calibration 6
Compatible sensors and accessories 9
Appendix A. Specifications
Range and Resolution 13
Quantum Sensors 13
Pyranometer 13
Photometric Sensor 13
Unit Conversions 14
Appendix B. Warranty
iii

Section 1.
1
Operation summary
The LI-250A Light Meter displays measurements from
LI-COR radiation sensors, including the LI-190R,
LI-191R, LI-192SA, LI-193SA, LI-200R, and LI-210R. It is
compatible with all LI-CORlight sensors that have a BNC
connector. The LI-250A provides high-resolution reading
and conversion of microamp signals from the attached
light sensor into suitable light measurement units. The
LI-250A does not have a specific calibration; calibrations
are associated with the attached light sensor.
Configuration mode vs. measurement mode
The LI-250A has two modes of operation: Configuration
Mode, where you enter calibration multipliers for light
sensors, and Measurement Mode, where the LI-250A makes
measurements. Press the Cal key to switch between modes.
Most of the keys on the 5-button keypad have two func-
tions. The active function depends on whether the
LI-250A is in measurement mode or configuration mode.
In measurement mode, the keys perform the upper func-
tion on each button (in green); in configuration mode,
the keys perform the lower function (in white).

Making measurements
Making measurements
1Attach the desired sensor.
2Power on the meter.
Press and hold the ON key for 2 seconds, and then
release. You will be in measurement mode.
3Press CAL to enter configuration mode.
4Press UNITS until the label on the display matches
the sensor type.
lFor Quantum Sensors, select µmol (actual units are
µmol s-1 m-2)
lFor a Pyranometer, select W m-2 (actual units are
Watts m-2)
lFor a Photometric Sensor, select Lux or Klux (actual
units are Lux or Kilolux)
Readings will be incorrect if the selected units do not
match the sensor that is connected to the meter.
5Press the up or down (▲,▼) key to change the
displayed multiplier until it matches the multiplier
for your sensor.
Press and hold the arrow key to scroll rapidly. The mul-
tiplier is on the calibration sheet under For use with
LI-COR handheld meters and loggers.
6Press CAL again to store the displayed multiplier.
The LI-250A is ready for measurements.
2

Making measurements
If you want to store a second calibration multiplier (either
for a second sensor or the In Water and In Air multipliers
for the LI-192 and LI-193 Underwater Quantum Sensors)
press CAL, then press MULT SELECT to switch to the second
multiplier. Press the arrow key to change the value of the
multiplier, and then press CAL to save it. The multiplier in
effect is the one displayed when you press CAL to exit con-
figuration mode.
Note: Pressing MULT SELECT before pressing CAL dis-
cards any changes you have made to the multiplier cur-
rently shown on the display.
Pressing CAL when in measurement mode will display the
multiplier in current use. The multiplier displayed when
CAL is pressed again will be stored as the active multiplier,
whether you have changed it or not.
While in measurement mode, press HOLD to retain the cur-
rent reading on the display. Press HOLD again to restore
live readings. Press AVG to begin a 15 second average,
which will be displayed until you press the HOLD key to
resume measurements. Press and release the OFF button to
power off the LI-250A. It will automatically shut off after
25 minutes of inactivity in measurement mode.
Caution: The LI-250A is weather resistant. However,
protect the meter from immersion or prolonged contact
with water, especially in marine environments. Water
damage is not covered under the warranty.
3

Power requirements
Power requirements
Power is supplied by one 9-volt battery. 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. Instruments are fitted with a snap-on connector;
simply align the male and female contacts and snap onto
the battery.
Although typical battery life is more than 150 hours of
continuous operation, it is dependent upon the storage
temperature. Do not store the LI-250A at high tem-
peratures.
In some instances, the internal storage is not retained
when the batteries are removed or when the batteries
become discharged. If the LI-250A is reading 0.0 after
replacing the batteries, check the multipliers stored in the
instrument and verify that they are correct for each sensor.
Re-enter them if necessary.
4

Section 2.
5
Overview of compatible sensors
The LI-250A is compatible with all LI-COR radiation
sensors that have a BNC connector (e.g., LI-200R-BNC or
older LI-200SA sensors). It is important that the LI-250A
be properly configured for the specific sensor used. A
quantum sensor measures photosynthetically active radi-
ation (µmol s-1 m-2 of PAR), a pyranometer measures solar
radiation (W m-2), and a photometric sensor measures illu-
minance (lux). It is not possible for a pyranometer to read
out in units of lux. If you want the LI-250A to display
units of lux, you must use the photometric sensor.
Recalibration of all LI-COR radiation sensors is recom-
mended every two years. The LI-250A does not need to be
recalibrated.
Overview of radiation sensor calibration
All LI-COR radiation sensors produce a current pro-
portional to the radiation intensity. During factory cal-
ibration, sensor output (in microamps) is measured while
the sensor is exposed to a standard lamp of known intens-
ity. The sensor output at this intensity has general units of
microamps per radiation unit and is called the Calibration