Extech 401025 Operating Manual

User's Manual

Model 401025
Digital Light Meter

Introduction

Congratulations on your purchase of Extech’s Digital Light Meter. This professional meter,
with proper care, will provide years of safe reliable service.

Specifications

General Specifications

Display 0.5" (13 mm) LCD (Liquid Crystal Display).
Measurement Lux, Ft-candle (Fc).
Ranges Lux: 0 to 50,000 Lux, 3 ranges. Foot-candle: 0-5,000 Fc, 3

Sensor Exclusive photo diode & color correction filter, spectrum
Zero Adj. Manual adjustment.

Sampling Time Approx. 0.4 sec.
Response Time Fast: 0.25s; Slow: 1s
Over input indication Indication of "1 "
Analog Output 0.1 mV/1 digit, max. output :200mV.
Operating Temperature (32OF to 122OF).(0OC to 50OC).
Operating Humidity Less than 80% RH.
Power Supply 006P DC 9V battery
Power Current Approx. 2 mA DC
Weight 220 g / 0.52 LB
Dimension Main instrument: 6.4x2.8x1.2 inch (163x70x30mm).

Optional Accessories Vinyl pouch carrying case, 409996

Range Specifications

Lux
Range In-range Display Resolution Accuracy

2,000 Lux 0-1,999 Lux 1 Lux ± (5% + 2digits)
20,000 Lux 2,000-19,990 Lux 10 Lux ± (5 % + 2digits)
50,000 Lux 20,000-50,000 Lux 100 Lux ±- (5 % + 2digits)

Foot-candle (Fc)
Range In-range Display Resolution Accuracy

200 Fc 0-199.9 Fc 0.1 Fc ± (5% + 2digits)
2,000 Fc 200-1,999 Fc 1 Fc ± (5% + 2digits)
5,000 Fc 2,000-5,000 Fc 10 Fc ± (5% + 2digits)

Frequency Spectrum

1

0.8

0.6

0.4

0.2
0

300 400 500 600 700 800

ranges.
designed to meet C. I. E.

Sensor Probe: 3.2x2.2x0.5 inch (85x55x12 mm).

Wavelength (nm)

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Meter Description

1. LCD Display

2. Data Hold Switch

3. Power Off/Range Switch

4. Analog Output Terminal

5. Battery Compartment (rear)

6. LUX/Fc Switch & Response Switch

7. Light Sensor

8. Zero adjust

8
5

Operation

1. Select Units (Lux or Ft-candle) and Response Time (Fast or Slow) on the slide
switch. Typical selection is Slow and Fc using the gray lettering.

2. Select the maximum range on the "Range Switch"

3. Hold the "Light Sensor" so that the sensor faces the light source to be measured.

4. The Display will indicate measured values. Use a range display multiplier if on the
Lux 20,000 and 50,000 ranges or on the Fc 5000 range.

5. To "hold" a measurement, slide the "Data Hold Switch" to the "hold" position. The
reading will "freeze" in the display until the "Data Hold Switch" is released.

Note 1: An Over Range indication is a display of "I ". If this occurs, switch to a higher

range.

Note 2: For measurements made on the Fc 5000 range, the displayed reading must be

multiplied by 10.

Note 3: For measurements made on the Lux 20000 or 50000 range, the displayed

reading must be multiplied by 10 and 100 respectively.

Note 4: The meter will indicate values above the maximum ranges. The accuracy of

these measurements is unknown.

Range Display Multipliers

Range Units Multiplier

200 Fc Direct reading
2000 Fc & Lux Direct reading
5000 Fc Reading x10
20,000 Lux Reading x10
50,000 Lux Reading x100

Example: If a measurement on the 5000 Fc range displays 350, then the actual
measured value is; 350 X 10 = 3500 Fc.

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Lux

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1
2
3

6
4

7

Selecting a Measurement Range

The meter has three measurement ranges (0-200, 0-2000, and 0-5000 Fc) and (0-2000, 0­20000, and 0-50000) Lux). The proper range selection will produce the most accurate
reading. Always select the range that produces the maximum number of digits without
exceeding the maximum count for that particular range. For example, a reading of 1456 Fc
should be read on the 0 - 2000 range, not the 0-5000 range.

Zero procedure

The meter zero (display with no light input) may change with time. Occasional checking and
adjustment may be required.

1. Completely cover the sensor to block out any light.

2. Set the range switch to the lowest Lux or Fc range

3. Using a small screwdriver, adjust the “Zero” control for a zero display. The last digit
may change slightly. This is normal and does not affect the accuracy of the meter.

Analog Output

The analog output jacks on the front panel produce a 0.1mV DC per digit signal that can be
used for recording or datalogging purposes.

Lighting Type Correction Factors

The 401025 light meter is calibrated under a precise "Standard tungsten light source of

O

K". If the meter is to be used under a different type of light the correction factor of from

2856
the table below should be applied to the readings obtained.

Mercury Lamp x1.14
Fluorescent Lamp X0.92 to 1.12
Daylight x1.00
Sodium x1.22
Metal Halide x1.00

Replacing the Battery

When the left corner of the LCD display shows "LO BAT", it indicates the battery output is
below the design limit and the battery needs to be replaced. However, reliable measurement
can still be taken for another few hours before the tester becomes inaccurate.

1. Open the Battery Cover at the back of tester and remove the battery.

2. Replace with a 9V battery and install the cover.

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Calibration and Repair Services

Extech offers complete repair and calibration services for all of the products we sell. For
periodic calibration, NIST certification or repair of any Extech product, call customer service
for details on services available. Extech recommends that calibration be performed on an
annual basis to insure calibration integrity.

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 on 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 [phone] ext. 210 for authorization or visit our
website at www.extech.com
number). 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.

(click on ‘Contact Extech’ and go to ‘Service Department’ to request an RA

Copyright ©

2001 Extech Instruments Corporation. All rights reserved including the

right of reproduction in whole or in part in any form.



Support Hotline [phone]

Tech support: Ext. 200; Email: [e-mail]
Repair/Returns: Ext. 210; Email: [e-mail]

Website: www.extech.com

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401025 Ver. 2.1 07/05

Appendix A: Typical Light Levels

Lux Foot
Factories Home

20-75 2-7 Emergency Stairs,
75-150 7-15 Exit/Entrance
150-300 15-30 Packing Work 200-300 20-30 Drawing Room,
300-750 30-75 Visual Work:
750-

1,500
1,500­3,000
Office Restaurant
75-100 7-10 Indoor Emergency

100-200 10-20 Corridor Stairs 150-300 15-30 Entrance, Wash
200-750 20-75 Conference,
750-

1,500
1,500­2,000
Store Hospital
75-150 7-15 Indoors 30-75 3-7 Emergency Stairs
150-200 15-20 Corridor/Stairs 75-100 7-10 Stairs
200-300 20-30 Reception 100-150 10-15 Sick Room,

300-500 30-50 Display Stand 150-200 15-20 Waiting Room
500-750 50-75 Elevator 200-750 20-75 Medical Exam

750­1,500
1,500­3,000

Candles

75-150 Typesetting:
150-300 Electronic Assembly,

75-150 Clerical Work 750-1,500 75-150 Show Window
150-2000 Typing, Drafting

75-150 Show Window,
150-300 Storefront, Show

Lux Foot

Warehouse
Passages

Production Line
Inspection Work
Drafting

Stairs

Reception Room

Packing Table
Window

100-150 10-15 Washing
150-200 15-20 Recreational

300-500 30-50 Makeup
500-1,500 50-150 Reading, Study
1,000-

2,000

75-150 7-15 Corridor Stairs

300-750 30-75 Cooking/Dining

750-1,500 75-150 Operating Room
5,000-

10,000

Candles

100-200 Sewing

500-1000 Eye Inspection

Activities
Table

Room
Room

Warehouse

Room

Appendix B - Common Terms and Conversion Factors

Illuminance (Visible Flux Density)

Luminance (Visible Flux Density per Solid Angle)
Luminous Intensity (Visible Flux per Solid Angle) 1 lm/sr = 1 candella

Luminous Flux ( Visible Flux) 1 lumen (lm) =

1 lm/m2 =

1 lm/m2/sr = 1 candela/m2

1 lux (lx)
10-4 lm/cm2
10-4 phot (ph)

9.290 x 10-2 lm/ft2

9.290 x 10-2 foot-candles

1.464 x 10-3 watts @ 555 nm

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