LED Light Meter
Model LT45
Congratulations on your purchase of the Extech LT45 LED Light Meter that measures light from LED
lamps in addition to fluorescent, metal halide, high-pressure sodium and incandescent sources.
The LT45 is capable of measuring the illumination of white, red, yellow, green, blue, and purple
LEDs up to 400,000 Lux (40,000 Fc).
The LT45 can also calculate luminous intensity (CD) using a distance-to-the-light value programmed
by the user in meters or feet units.
The LT45 can store up to 99 readings for later recall and includes Overload indication, Battery
status icon, Data hold, Maximum/Average/Minimum (MAX/MIN) tracking, push-button Zero
calibration adjustment, Auto Power off (with disable function), and auto ranging features.
This instrument is shipped fully tested and calibrated and, with proper use, will provide years of
reliable service. Please visit our website ( to check for the latest version of this
User Guide, Product Updates, and Customer Support.
Overload Indication: LCD screen will show “OL” at the upper left-hand corner
Battery strength status indication
Display Update Rate: 2.5 times per second
Spectral response near CIE luminous spectral efficiency ratings
Cosine Angle corrected
Conforms to JIS C 1609:1993 and CNS 5119 general class A Specifications
Measures the intensity of illumination of white, red, yellow, green, blue, and purple LED
light and all visible light in Lux or foot-candles
Calculates Luminous Intensity (CD)
Data hold freezes displayed reading
Maximum/Average/Minimum Memory Hold
Zero adjustment
Auto power off with disable function
Automatic range adjust optimizes accuracy and resolution
Manually store/recall up to 99 readings
Complete with light sensor, protective sensor cover, and coiled cable expandable to 59”
(1.5m), 9V battery, and hard shell case
LT45-EN v1.4 9/13
Do not operate the meter in environments where the following are present: explosive gases
(or materials), combustible gases (or materials), steam, or dust.
Please replace the battery immediately when the battery symbol
Do not touch the meter’s circuit board for any reason as static electricity or contamination
could damage the sensitive components.
For Indoor use only. This instrument was designed for pollution degree 2.
Operation Altitude: Up to 2000m (7000’).
appears on the LCD.
Meter Description
Display (LCD)
Lux/Fc/CD unit select button
MEM/READ button (for 99 reading memory)
Up arrow button and MAX/MIN/AVG button
Power and Auto Power OFF control button
Zero Calibration button
Data Hold and Light source select button
Down arrow button
Coiled sensor connection cable
10. Photo detector
Note: The battery and tripod mount are located
on the back of the meter
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Power ON-OFF
Momentarily press the Power button to power the meter. To power the meter OFF,
momentarily press the Power button again.
Taking Measurements
1. Switch the meter ON
2. Remove the sensor’s protective cover to expose the light sensor dome. The display should
switch ON, if not check that fresh batteries are installed.
3. The meter measures the intensity of the light (illuminance) that strikes the sensor dome in
foot candles and lux units (1 fc = 10.76 lux) displaying the measured value on the LCD.
4. Use the LUX/FC/CD button to select Lux or Foot candle units (CD, luminous intensity, is
explained in the dedicated section ‘Luminous Intensity’). When ‘OL’ is displayed, the
measurement exceeds the meter’s range capability.
5. Position the meter and light source so that the light strikes the sensor dome perpendicularly.
6. The meter’s LCD can show a value up to 3999 on the large digits and when more digits are
needed to represent the reading two additional (smaller) digits appear to the right of the
larger digits, e.g. 399900.
Momentary presses of the LUX/FC/CD button toggles Lux and FC (foot-candles) units. Press and
hold the button to enter the CD (luminous intensity) mode. Refer to ‘Luminous Intensity’ section
for further information.
Auto Power OFF
To save battery life the meter powers down automatically after approximately 5 minutes of
inactivity (no button presses).
Enable/Disable Auto Power Off
With the meter ON, press and hold the Power button until the APO clock symbol switches
OFF (the Auto Power OFF utility is now disabled and the user must manually switch the meter
off). To re-enable the Auto Power OFF utility, repeat this process. The Clock symbol will switch
ON when the Auto Power OFF utility is re-enabled.
Zero Calibration
1. Ensure that the protective cover is attached to the light sensor.
2. Power the meter and the LCD should display ‘0’.
3. Momenarily press the “ZERO” button and the ADJ (adjusting) icon will switch ON indicating
that the zero adjustment (calibration) is working. When the calibration is finished, the ADJ
icon will switch OFF and the meter will return to the normal operating mode.
4. If the protective cap is not covering the sensor when the ZERO calibration is started the LCD
display will read “CAP”. In this case, please cover the sensor with the cap and restart this
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MAX/AVG/MIN Memory Mode
The meter can record the maximum, minimum, and average readings as described below:
1. Momentarily press the MAX/AVG/MIN
button and the meter will begin to track the
maximum/average/minimum measurements; the “MIN” icon will display on the LCD
indicating that the meter is now displaying the minimum reading. The reading will not
change until a lower reading is registered.
2. Press the
button again to switch from “MIN” to “MAX” where the meter will show the
maximum measurement value. The “MAX” icon will be displayed on the LCD.
3. Press the
button again to change the mode from “MAX” to “AVG”, where the meter will
show the average of the readings taken since the
button was first pressed. The “AVG”
icon will be displayed.
4. Press the
button again to switch from “AVG” back to “MIN”.
To exit this mode, press and hold the
button for at least 2 seconds. The MAX/AVG/MIN icons
should all be switched OFF when the unit returns to the normal operating mode.
Memory Record/Read Mode
1. Momentarily press the Mem/Read button to store a reading. The LCD will display a small ‘M’
icon on the lower left-hand area of the LCD along with the memory location number (1 to
99) representing the storage location for the recorded reading. Up to 99 readings can be
2. To review (read) the stored readings, press and hold the Mem/Read button until the ‘MEM’
icon appears at the top of the LCD. Now use the arrow buttons to scroll through the stored
readings. The small ‘M’ icon and the memory location counter (1 to 99) will be shown on the
lower left-hand corner of the LCD while the main display digits show the stored reading for
the selected memory location.
3. To store an average (AVG) reading, first access the AVG mode (See MIN/MAX/AVG section of
this guide) and while an average reading is displaying (AVG icon switched ON), momentarily
press the Mem/Read button for one second. The LCD will display ‘AVG M’ and the memory
location number (1 to 99) indicating that an average reading has been stored in the
numbered memory location.
4. When a stored reading is an AVG value, the screen will display ‘AVG’ on the lower left-hand
5. Momentarily press the Mem/Read button to exit the Memory mode and return to the
normal operating mode.
6. To clear all 99 memory locations: With the meter switched OFF, press and hold the
Mem/Read and On/Off buttons simultaneously for two seconds. The meter will switch ON
and the screen will display “CLr” indicating that all of the 99 memory locations have been
Data Hold
Press the Hold button to freeze the displayed reading (the ‘HOLD’ icon will switch ON). Press the
button again to release the held reading (the ‘HOLD’ icon will switch OFF).
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Luminous Intensity (CD) Measurements
1. Press the On/Off button to turn power ON.
2. Press and hold the LX/FC/CD button until the meter’s unit designator switches to CD.
3. Use the arrow buttons to select ft (feet) or m (meter) units to represent the distance the
sensor will be from the light source.
4. Momentarily press the LX/FC/CD button; the smaller digits (lower-right hand corner of LCD)
will switch ON, these digits represent the distance to the light source.
5. Use the arrow buttons to set the distance from the center of the lamp to the measurement
base level. Press and hold an arrow button to scroll quickly.
6. Momentarily press the LX/FC/CD button.
7. Remove the protective sensor cap and place the sensor perpendicular to the light at the
programmed distance.
8. Read the Luminous Intensity calculation on the meter’s LCD display.
9. Press and hold the LX/FC/CD button to exit this mode.
 Luminous Intensity = illumination (Lx) x distance (ft or m )
 The programmable distance range is 0.01 ~ 30.47 m (0.01 ~ 99.99 ft.)
Light Source (L.S.) Selection
There are 10 light source selections (L0 – L9) each having a unique calibration correction factor
(multiplier). See the Light Source Factors list below. The multipliers for locations L0 through L6
are fixed for the lighting types listed. Locations L7 through L9 are extra locations that the user
can customize (with a multiplier from 0.001 to 1.999). To change the light source (L.S.) selection:
1. Press and hold the Hold/LS button for 2 seconds. The light source code, at the bottom center
of the LCD, will flash. Use the arrow buttons to select L0 through L9. The location’s multiplier
(correction factor) will be shown to the right of the Lx value (L8…1000, for example).
2. To customize a location, select L7, L8 or L9 and, once selected, momentarily press the
Hold/LS button to enter the multiplier programming mode. Now use the arrow keys to
change the multiplier. Press and hold an arrow button to scroll faster.
3. When finished, press and hold the Hold/LS button for at least 1 second to confirm the edit
and exit this mode.
Light Source Factors
L0: Standard light source: 1.00.
L1: LED white daylight: 0.99.
L2: LED RED light: 0.516.
L3: LED AMBER (YELLOW) light: 0.815.
L4: LED GREEN light: 1.216.
L5: LED BLUE light: 1.475.
L6: LED PURPLE light: 1.148.
L7~L9: Programmable User Custom Locations (preset to 1.00)
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Measurement Considerations and User Tips
For maximum accuracy allow the light being measured to fall directly on the sensor as
perpendicular as possible with a minimal angle of incidence.
When the meter is not in use, please keep the protective cap in place, covering the light
sensor. This will prolong the life of the sensor.
When the meter is to be stored for long periods, please remove the battery and store it
separately. Batteries can leak and cause damage to the meter’s components.
Avoid areas of high temperature and humidity when using this instrument.
Battery Replacement and Maintenance
Cleaning and storage
1. The white plastic sensor dome should be cleaned with a damp cloth when necessary. Use
only a mild soap if needed. Do not use solvents, abrasives, or harsh detergents to clean the
2. Store the meter in an area with moderate temperature and relative humidity.
Battery Replacement
When the battery power decreases to a critical level, the battery symbol will appear as empty on
the LCD. Replace the 9V battery located in the rear battery compartment. The battery
compartment slides easily downward for removal (in the direction of the printed arrow on the
rear of the meter). Ensure that the compartment cover is securely fastened before using the
Battery Safety Reminders
o Please dispose of batteries responsibly; observe local, state, national regulations.
o Never dispose of batteries in a fire; batteries may explode or leak.
LT45-EN v1.4 9/13
Sampling rate
2.5 times per second (digital display)
6-digit LCD with battery icon, measurement overload, and
other function indicators
Sensor (detector)
Silicon photodiode with spectral response filter and cosine
Ranges and Resolution
Lux: 399.9, 3999, *39999, *399999
Foot-candles: 39.99, 399.9, 3999, *39999
*Above 3999, the LCD uses smaller digits on the right side
(1 Fc = 10.76 Lux)
The meter automatically ranges the display
± (3% of reading + 3 digits) up to 500 Lux
± (3%) above 500 Lux
Calibrated to standard incandescent lamp 2856oK at an
ambient temperature of 73oF (23oC)
±6% for other visible light sources
Angle deviation from cosine
30 ○
80 ○
LED Types
Operating conditions
Storage Temperature/RH
Battery status indication
Power supply
Auto Power OFF
Meter measures white, red, yellow, green, blue, purple LED light
Temperature: 41 to 104oF (5 to 40oC); Humidity: < 80% RH
14 to 140oF (-10 to 60oC); Humidity: < 70% RH
Battery symbol appears empty when battery voltage reaches critical level
9V battery
Meter powers down after 5 minutes of inactivity (can be defeated)
Meter: 1.5 x 2.2 x 5.1” (38 x 55 x 130mm)
Sensor: 9.8 x 2.2 x 3.1” (25 x 44 x 80mm)
Cable length: 4.9’ (1.5m)
Approx. 8.8 oz. (250g) with battery installed
LT45-EN v1.4 9/13
FLIR Systems, Inc. warrants this Extech Instruments brand device to be free of defects in parts and workmanship for one year
from date of shipment (a six month limited warranty applies to sensors and cables). If it should become necessary to return the
instrument for service during or beyond the warranty period, contact the Customer Service Department for authorization. Visit
the website for contact information. A Return Authorization (RA) number must be issued before any product is
returned. The sender is responsible for shipping charges, freight, insurance and proper packaging to prevent damage in transi t.
This warranty does not apply to defects resulting from action of the user such as misuse, improper wiring, operation outside of
specification, improper maintenance or repair, or unauthorized modification. FLIR Systems, Inc. specifically disclaims any implied
warranties or merchantability or fitness for a specific purpose and will not be liable for any direct, indirect, incidental or
consequential damages. FLIR’s total liability is limited to repair or replacement of the product. The warranty set forth above is
inclusive and no other warranty, whether written or oral, is expressed or implied.
Calibration, Repair, and Customer Care Services
FLIR Systems, Inc. offers repair and calibration services for the Extech Instruments products we
sell. NIST certification for most products is also provided. Call the Customer Service Department for
information on calibration services available for this product. Annual calibrations should be
performed to verify meter performance and accuracy. Technical support and general customer
service is also provided, refer to the contact information provided below.
Support Lines: U.S. (877) 439-8324; International: +1 (603) 324-7800
Technical Support: Option 3; E-mail:
Repair & Returns: Option 4; E-mail:
Product specifications are subject to change without notice
Please visit our website for the most up-to-date information
FLIR Commercial Systems, Inc., 9 Townsend West, Nashua, NH 03063 USA
ISO 9001 Certified
Copyright © 2013 FLIR Systems, Inc.
All rights reserved including the right of reproduction in whole or in part in any form
LT45-EN v1.4 9/13
FLIR Systems, Inc. garantit que cet appareil Extech Instruments est exempt de défauts matériaux et de fabrication pendant un
an à partir de la date d’envoi (une garantie limitée de six mois s’applique aux capteurs et aux câbles). Si le renvoi de l’appareil
pour réparation devient nécessaire durant ou après la période de garantie, contactez le service client pour autorisation. Pour
obtenir les coordonnées, visitez le site Web suivant : Un numéro d’autorisation de retour (AR) doit être délivré
avant tout retour de produit. L’expéditeur prend à sa charge les frais d’expédition, le fret, l’assurance et l’emballage correct de
l’appareil afin de prévenir toute détérioration durant le transport. Cette garantie ne s’applique pas aux dommages imputables à
l’utilisateur, tels que l’usage impropre ou abusif, un mauvais câblage, une utilisation non conforme aux spécifications, un
entretien ou une réparation incorrecte, ou toute modification non autorisée. FLIR Systems, Inc. déclinera spécifiquement toute
garantie ou qualité marchande ou aptitude à l’emploi prévu, et ne sera en aucun cas tenu responsable pour tout dommage
conséquent, direct, indirect ou accidentel. La responsabilité totale de FLIR est limitée à la réparation ou au remplacement du
produit. La garantie définie ci-dessus est inclusive et aucune autre garantie, écrite ou orale, n’est exprimée ou implicite.
Calibrage, réparation et services après-vente
FLIR Systems, Inc. offre des services de calibrage et de réparation pour les produits Extech
Instruments que nous commercialisons. Nous fournissons également une certification NIST pour la
plupart des produits. Contactez notre service client pour toute information sur les services de
calibrage disponibles pour ce produit. Un calibrage doit être effectué chaque année pour vérifier
les performances et la précision du mètre. Nous offrons également une assistance technique et un
service à la clientèle. Veuillez vous reporter aux coordonnées fournies ci-dessous.
Lignes d’assistance: États-Unis (877) 439-8324; international: +1 (603) 324-7800
Service d’assistance technique : Option 3 ; E-mail :
Réparations et retours : Option 4 ; E-mail :
Les spécifications produit sont sujettes à modifications sans préavis.
Pour les toutes dernières informations, veuillez visiter notre site Web.
FLIR Commercial Systems, Inc., 9 Townsend West, Nashua, NH 03063 USA
Certifié ISO 9001
Copyright © 2013 FLIR Systems, Inc.
Tous droits réservés, y compris la reproduction partielle ou totale sous quelque forme que ce soit.
LT45-EN v1.4 9/13
FLIR Systems, Inc., garantiza este dispositivo marca Extech Instruments para estar libre de defectos en partes o mano de obra
durante un año a partir de la fecha de embarque (se aplica una garantía limitada de seis meses para cables y sensores). Si fuera
necesario regresar el instrumento para servicio durante o después del periodo de garantía, llame al Departamento de Servicio a
Clientes para obtener autorización. Visite para Información de contacto. Se debe expedir un número de
Autorización de Devolución (AD) antes de regresar cualquier producto. El remitente es responsable de los gastos de embarque,
flete, seguro y empaque apropiado para prevenir daños en tránsito. Esta garantía no se aplica a defectos resultantes de las
acciones del usuario como el mal uso, alambrado equivocado, operación fuera de las especificaciones, mantenimiento o
reparación inadecuada o modificación no autorizada. FLIR Systems, Inc., rechaza específicamente cualesquier garantías
implícitas o factibilidad de comercialización o idoneidad para cualquier propósito determinado y no será responsable por
cualesquier daños directos, indirectos, incidentales o consecuentes. La responsabilidad total de FLIR está limitada a la
reparación o reemplazo del producto. La garantía precedente es inclusiva y no hay otra garantía ya sea escrita u oral, expresa o
Servicios de calibración, reparación y atención a clientes
FLIR Systems, Inc., ofrece servicios de reparación y calibración para los productos que vendemos
de Extech Instruments. Además ofrecemos certificación NIST para la mayoría de los productos.
Llame al Departamento de Servicio al Cliente para solicitar información de calibración para este
producto. Para verificar el funcionamiento y precisión se debe realizar la calibración anual. Además
se provee Soporte Técnico y servicios generales al cliente, consulte la información de contacto en
Líneas de soporte: EE.UU. (877) 439-8324; Internacional: +1 (603) 324-7800
Soporte Técnico Opción 3; correo electrónico:
Reparación / Devoluciones: Opción 4; correo electrónico:
Las especificaciones del producto están sujetas a cambios sin aviso
Por favor visite nuestra página en Internet para la información más actualizada
FLIR Commercial Systems, Inc., 9 Townsend West, Nashua, NH 03063 USA
Certificado ISO 9001
Copyright © 2013 FLIR Systems, Inc.
Reservados todos los derechos, incluyendo el derecho de reproducción total o parcial en cualquier medio
LT45-EN v1.4 9/13
Typical Light Levels
Emergency Stairs, Warehouse
Exit/Entrance Passages
Packing Work
Visual Work: Production Line
Typesetting: Inspection Work
Electronic Assembly, Drafting
Indoor Emergency Stairs
Corridor Stairs
Reception Room
75-150 Clerical Work
150-2000 Typing, Drafting
Display Stand
Show Window,
Packing Table
Storefront, Show Window
Drawing Room,
Reading, Study
Corridor Stairs
Wash Room
Cooking Room,
Dining Table
Show Window
Emergency Stairs
Sick Room,
Waiting Room
Medical Exam Room
Operating Room
500-1000 Eye Inspection
Spectral Sensitivity
Peak sensitivity wavelength: 550nm
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