User's Guide
Digital Light Meter
Model 403125
403125 V3.1 9/06 2
Warranty
EXTECH INSTRUMENTS CORPORATION warrants this instrument 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 at
(781) 890-7440 ext. 210 for authorization or visit our website www.extech.com for contact
information. A Return Authorization (RA) number must be issued before any product is
returned to Extech. The sender is responsible for shipping charges, freight, insurance and
proper packaging to prevent damage in transit. 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. Extech
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.
Extech'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.
Introduction
Congratulations on your purchase of the Extech 403125 Digital Light Meter. This
portable, compact light meter provides lux and fc measurements. This meter includes a
backlit LCD display and offers PEAK HOLD and DATA HOLD functionality. This meter is
shipped fully tested and calibrated and, with proper use, will provide years of reliable
service.
Safety Instructions
It is recommended that the user read and understand the safety and operational
instructions before using the light meter. Please read the following WARNINGS:
• To avoid electrical shock do not operate this meter in wet or damp conditions.
• Do not immerse the meter in liquid. For cleaning instructions, refer to the
maintenance section of this manual.
• To avoid injury and fire hazard, do not use this meter in potentially explosive
environments.
• To avoid eye injury, wear eye protection if there is the possibility of exposure
to high intensity light rays.
• Cover the sensor head when not in use. This will extend the life of the photo-
diode employed in the sensor head.
403125 V3.1 9/06 3
Specifications
General Specifications
Display 3 ½ digit backlit LCD display (reads 0 to 1999)
Over range indication OL (over load) is displayed
Measurement rate 2.5 readings per second (nominal)
Battery power Four (4) 1.5V ‘AAA’ batteries
Battery life 200 hours typical
Low battery indication Battery symbol is displayed when the battery power drops
below the operating voltage
Operating conditions 32 to 122
o
F (0 to 50oC) < 70% Relative Humidity
Storage conditions -4 to 140
o
F (-20 to 60oC) < 80% Relative Humidity (with
batteries removed)
Analog output 0.1mVDC per display digit
Dimensions 6.7 x 1.7 x 1.6" (170 x 44 x 40mm)
Weight Approx. 7.76 oz. (220g) with batteries
Electrical Specifications
Ranges 20, 200, 2000, 20,000 fc and lux (note that the 20,000 range is
displayed in the x10 mode, meaning that the display must be
multiplied by 10).
Resolution 0.01 lux/fc maximum
Accuracy 20, 200 ranges: ± (5% of reading + 10 digits)
2000, 20,000 ranges: ± (3% of reading + 10 digits)
Accuracy note: Stated accuracy for ± 9
o
F at 73oF (±5oC at
23
o
C) < 70% Relative Humidity
Spectral response CIE photopic
Note: The CIE photopic curve is an international standard for
the color response of the average human eye. The CIE
standard illuminant ‘A’ is defined as a gas-filled Tungsten-
filament lamp operating at a correlated color temperature of
2856K.
Peak Hold response 50ms minimum response time for the measurement of a light
pulse
Acceptance angle f ’
2
< 2% cosine corrected (150o)
Units conversion 10.764 fc = 1 lux (lumens/meter
2
)
0.0929 lux = 1 fc (lumens/foot
2
)
Temperature Coefficient 0.056 times the specified accuracy per
o
F (< 64.4oF or >
82.4
o
F)
0.1 times the specified accuracy per
o
C (< 18oC or > 28oC)
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