Extech Extech LT300 Manual

User Guide

Digital Light Meter

Model LT300

99 Washington Street
Melrose, MA 02176

Phone [phone]
Toll Free 1-800-517-8431

Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176

FAX [phone] - TestEquipmentDepot.com

Visit us at www.TestEquipmentDepot.com

Back to the Extech LT300 Product Info Page

Introduction

Congratulations on your purchase of the Extech LT300 Digital Light Meter. The LT300
measures light level (illuminance) to 200,000 Lux (20,000 Fc). The LT300 offers a backlit
display, MAX/MIN, Data Hold, Relative, Peak, and Reset features. This instrument is
shipped fully tested and calibrated and, with proper use, will provide years of reliable
service.

Meter Description

1. Sensor cable

2. Analog bargraph

3. Numerical display

4. RANGE button

5. ON/OFF button

6. MAX/MIN button

7. RESET button

8. LCD Backlight button

9. LUX button

10. Fc foot candle button

11. Protective rubber jacket

12. RELATIVE button

13. Data HOLD button

14. PEAK button

15. Photo sensor dome

Notes: Protective sensor cap not shown. Battery compartment, Tilt Stand, and Tripod Mount are located on the rear

of the instrument. The protective rubber jacket must be removed from meter to access battery compartment.

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LT300 V2.0 6/06

Operation

Light sensor

1. The light sensor is permanently
attached to the meter by the coiled
cable.

2. Remove the protective cap by
unsnapping it to expose the white
domed light sensor. When the sensor’s protective cap is removed, the white domed
light sensor lens will begin to capture light. Replace the cap when the meter is not in
use.

Turn Power ON or OFF

Press the button to turn power on or off. If the display does not switch on, check that
the 9V battery is installed and is fresh.

Selecting Lux or Foot candle units of measure

Press the LUX button to select lux units or the Fc button to select foot candle units.

Measurement Procedure

1. Remove the protective cap from the sensor so that the white domed light sensor is
exposed to the light. For overhead lighting, the sensor can be placed on a desk or
table top. A tripod mount and a tilt stand are located on the rear of the meter for
convenience.

2. The display will indicate the light level in Fc or Lux.

3. Press the RANGE button to select the range that provides the maximum resolution. If
the ‘OL’ appears the light measurement is out of range. Select another range using the
RANGE button.

4. Press the backlight button to illuminate the LCD display if needed.

MAX/MIN

The Max/Min function allows for recording and display of the maximum and minimum light
levels over time.

1. Press the MAX/MIN button. The MAX display icon will appear and meter will now
display and hold only the highest reading. The display will update only when a higher
reading is measured.

2. Press MAX/MIN button. The MIN display icon will appear and meter will now display
and hold only the lowest reading. The display will update only when a lower reading is
measured

3. Press MAX/MIN again. The MAX MIN display icons will appear flashing and meter will
now display the current reading, but will continue to record the highest and lowest
values.

4. Press MAX/MIN again to cycle through MAX and MIN displays.

5. To exit the MAX MIN mode, press and hold the MAX/MIN button until the MAX and

MIN icons completely disappear.

Data Hold

Press the HOLD button to freeze the displayed reading. The ” MANU HOLD” hold icon will
appear on the display. Press the HOLD button again to return to normal operation. When
the Data Hold function is enabled the analog bar graph will continue to display level
changes.

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LT300 V2.0 6/06

Peak Hold

The Peak Hold feature allows the meter to captures light pulses that rise or fall down to
10µs.

1. Press and hold the PEAK button until CAL appears in the display.

2. Momentarily press the PEAK button. The ‘P

MAX’ icon will appear on the LCD. The

meter will then measure and display any light pulses. The display will hold the results
until a higher pulse appears.

3. Press the PEAK button again to display the “P

4. To exit the Peak Hold mode, press and hold the PE AK button until the ‘P

MIN” values.

MAX’ or ‘PMIN’

icon disappears.

Relative mode

Measurements can be displayed as a difference between the measured light level and a
stored reference value. To store a reading as a reference, press the REL button when the
desired reference measurement is on the LCD (the REL icon will switch on). All
subsequent displayed readings will be “relative” to the stored reference value. For
example, if the reference value is 100 and the actual light level is 125, the meter will
display 25. To view the reference value, press the REL button again so that the REL icon
begins to flash. The displayed value will be the reference value. To exit the Relative mode,
press and hold the REL button until the REL icon disappears.

RESET

Press the RESET button to clear the memory and exit from REL, HOLD, PEAK and
MAX/MIN. The RESET will also reset the auto power off timer.

Backlight

Press the “ “ button to turn the backlight on. Press again to turn it off.

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 dome.

2. Store the meter in an area with moderate temperature and humidity (refer to the
operating and storage range in the ‘Specifications’ section).

Battery Replacement

When the battery power begins to fail the low battery symbol “
Replace the 9V battery by first removing protective jacket that encases the meter. Remove
the rear (center) battery compartment screw to access the battery compartment. Ensure
that the compartment cover is securely fastened and that the protective jacket is properly
installed before using the meter.

”will appear on the LCD.

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LT300 V2.0 6/06

Specifications

Ranges and Resolution Accuracy

Lux

40.00, 400.0, 4000, 40.00k, 200.0kLux ± (5% Rdg + 0.5% Full Scale)
Foot candle (Fc)

40.00, 400.0, 4000, 20.00kFc ± (5% Rdg + 0.5% Full Scale)

General Specifications

Display Multi-function 3-3/4 (3999) digit LCD with Bargraph indicator
Over range indication LCD displays ‘OL’
Spectral response CIE photopic (CIE human eye response curve)
Spectral accuracy CIE V function (f
Measurement Repeatability ±2%
Temperature coefficient ±0.1% per
Sampling rate 13.3 times per second (bargraph); 1.3 times per second (digital

Photo detector Silicon photo-diode with spectral response filter
Peak Hold Capture light peaks to 10µS
Operating conditions Temperature: 32 to 104
Storage conditions Temperature: 14 to 140
Dimensions 6.5 x 3.0 x 1.7" (165 x 76 x 43mm)
Weight Approx. 14.2 oz. (403g) with battery installed
Low battery indication “
Power supply 9V battery

display)

” appears on the LCD

 ï 6%)

1

o

C

o

F (0 to 40oC); Humidity: < 80% RH

o

F (-10 to 50oC); Humidity: < 80% RH

99 Washington Street
Melrose, MA 02176

Phone [phone]
Toll Free 1-800-517-8431

Visit us at www.TestEquipmentDepot.com

Back to the Extech LT300 Product Info Page

Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176

FAX [phone] - TestEquipmentDepot.com

Appendix

Typical Light Levels

Lux Foot

Candles

Lux Foot

Candles

Factories Home

20-75 2-7 Emergency Stairs, Warehouse 100-150 10-15 Washing

75-150 7-15 Exit/Entrance Passages 150-200 15-20 Recreational
150-300 15-30 Packing Work 200-300 20-30 Drawing Room,
300-750 30-75 Visual Work: Production Line 300-500 30-50 Makeup

750-1,500 75-150 Typesetting: Inspection Work 500-1,500 50-150 Reading, Study

1,500-3,000 150-300 Electronic Assembly, Drafting 1,000-2,000 100-200 Sewing

Office Restaurant

75-100 7-10 Indoor Emergency Stairs 75-150 7-15 Corridor Stairs
100-200 10-20 Corridor Stairs 150-300 15-30 Entrance,

200-750 20-75 Conference,

300-750 30-75 Cooking Room,

Reception Room

750-1,500 75-150 Clerical Work 750-1,500 75-150 Show Window

1,500-2,000 150-2000 Typing, Drafting

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

750-1,500 75-150 Show Window,

750-1,500 75-150 Operating Room

Packing Table

1,500-3,000 150-300 Storefront, Show Window 5,000-10,000 500-1000 Eye Inspection

Spectral Sensitivity

R
e

1

l

a

t

0.8

i
v
e

0.6

R
e
s

0.4

p
o
n

0.2

s
e

400 450 500 550 600 650 700

0

- - - - - Light Meter Response

Wavelength (nm)

_____

CIE Response

Activities
Table

Wash Room
Dining Table

Warehouse

Room

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LT300 V2.0 6/06