Extech LT40 White LED Light Meter

User Manual

Product Code: 202305

Model LT40

Introduction

Congratulations on your purchase of the Extech LT40 LED Light Meter. This meter measures light intensity from white LED light sources. The LT40 can also measure light from fluorescent, metal halide, high-pressure sodium, and incandescent sources (for reference only, unspecified accuracy). The LT40 can measure light up to 40,000 Fc (400,000 Lux). This instrument is shipped fully tested and calibrated and, with proper use, will provide years of reliable service. Please visit our website (www.extech.com) to check for the latest version of this User Guide, Product Updates, and Customer Support.

Features

Overload Indication: The LCD will show OL.
Low battery indication.
Display Update Rate: 2.5 times per second.
Cosine Angle corrected.
Measures white LED light.
Measures the intensity of illumination in Lux or foot-candles.
Data hold freezes displayed reading.
Maximum/Average/Minimum reading Hold.
Zero Calibration adjustment.
Auto power off with disable function.
Auto range.

Safety

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 low battery symbol appears on the LCD.
Do not touch the meter's circuit board for any reason; 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 7000' (2000m).

Meter Description

Photo detector (remove protective cover to expose sensor)
Display (LCD)
Control push-buttons
Power Button: ON/OFF

Battery compartment and tripod mount are located on rear of instrument.

Push-Button Description

Lux/Fc units selector
Zero Calibration button
Maximum/Average/Minimum memory button
Data hold button

Operation

Power ON/OFF

Long press the Power button to power the meter. To power the meter OFF, short press the Power button.

Taking Measurements

Switch the meter ON and remove the sensor's protective cover to expose the light sensor dome. The display should switch ON; if not, check that batteries are installed and fresh.
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 this measured value on its LCD.
Position the meter and light source so that the light strikes the sensor dome straight on (perpendicular) with as little an angle as possible.
The meter's display can show a value up to 9999. However, for readings that represent measurements higher than this, the meter uses x10 or x100 feature. For example, to represent a measurement of 11,000 fc the meter will display 1100 with the x10 indicator.

Auto Power OFF

To save battery life, the meter powers down automatically after approximately 12 minutes of inactivity.

Enable/Disable Auto Power Off

While the meter is ON, long press the Power button to disable the Auto Power OFF utility (the Clock symbol ⚙️ will switch OFF). To enable the Auto Power OFF utility, repeat this process.

LUX/FC Button

Press the LUX/FC button to toggle between Lux and FC (foot-candles) measurement units.

MAX/MIN Button

The meter can record the maximum, minimum, and average readings as described below:

Short press the “MAX/MIN” button and the meter will begin to track the maximum/average/minimum measurements; the “MAX” icon will display at the top of the LCD window indicating that the meter is now showing the maximum reading. The reading will not change until a higher reading is registered.
Press the “MAX/MIN” button again to switch from “MAX” to “AVG”, where the meter will show the average measurement value. The “AVG” icon will be displayed above the displayed value.
Press the “MAX/MIN” button again to change the mode from “AVG” to “MIN”, where the meter will show the minimum value measured. The “MIN” icon will be displayed.
Press the “MAX/MIN” button again to switch from “MIN” back to “MAX”.
To exit this mode, hold the “MAX/MIN” 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.

HOLD Button

Press the HOLD button to freeze the current reading on the LCD. Press the HOLD button again to release the reading. In the Data Hold mode, HOLD is displayed on the LCD.

Zero Calibration Procedure

Ensure that the protective cap is attached to the light sensor.
Power the meter and the LCD should display '0'.
Short press the “CAL ZERO” button to perform the zero adjustment (CAL will appear on the display).
The CAL display will switch off when the calibration has been completed.
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 procedure.

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 over the light sensor. This will prolong the life of the sensor.
When the meter is to be stored for long periods, please remove the batteries and store them 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

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.
Store the meter in an area with moderate temperature and relative humidity.

Battery Replacement

When the battery power decreases to a critical level, the low battery symbol “⇐+Þ" will appear on the LCD. Replace the 2 x 1.5V AAA batteries located in the rear battery compartment.

Press and hold the battery compartment lock button (see diagram).
Slide the battery compartment cover off in the direction of the arrow.

Install two (2) 1.5V ‘AAAʼ batteries observing correct polarity and close the battery compartment. Ensure that the compartment cover is securely fastened before using the meter.

Specifications

Units	Range	Resolution	Accuracy
Lux	999.9	0.1	White LED: ±(3%reading) ±3 Lux up to 500 Lux ±(3%reading) >500 Lux Other (Non-White LED) light sources: ±(8% reading) Other (Non-LED) light sources: ±(8% reading)
	9,999	1
	99,990*	10
Foot candles	99.99	0.01	White LED: ±(3%reading) ±0.3 Fc up to 46 Fc ±(3%reading) >46 Fc Other (Non-White LED) light sources: ±(8% reading) Other (Non-LED) light sources: ±(8% reading)
	999.9	0.1
	40,000*	10

* Readings above 9999 use a x10 or x100 multiplier (1 Fc = 10.76 Lux)

Angle deviation from cosine characteristics
30°	±2%
60°	±6%
80°	±25%

General Specifications

Sampling rate: 2.5 times per second (digital display)
Photo detector: Silicon photodiode with cosine correction
Display: 4-digit LCD (maximum display: 9999) with low battery icon, measurement overload, and other function indicators
Auto Range: Meter automatically ranges the display
Operating conditions: Temperature: 41 to 104°F (5 to 40°C); Humidity: < 80% RH
Storage conditions: Temperature: 14 to 140°F (-10 to 60°C); Humidity: < 70% RH
Low battery indication: ⇐+Þ appears on the LCD when battery voltage falls critically low
LED Type: White LED light
Power supply: 2 x 1.5V 'AAA' batteries
Battery life: Approximately 200 hours
Auto Power OFF: Meter switches OFF after 12 minutes of inactivity
Dimensions: 5.2 x 1.9 x 0.9" (133 x 48 x 23 mm)
Weight: 8.8 oz. (250g) including batteries

Appendices

Typical Light Levels (1 Fc = 10.76 Lux)

Lux	Foot Candles	Factories	Lux	Foot Candles	Home
20-75	2-7	Emergency Stairs, Warehouse	100-150	10-15	Washing Activities
75-150	7-15	Exit/Entrance Passages	150-200	15-20	Recreational Drawing Room, Table
150-300	15-30	Packing Work	200-300	20-30	Makeup
300-750	30-75	Visual Work: Production Line	300-500	30-50	Reading, Study
750-1,500	75-150	Typesetting: Inspection Work	500-1,500	50-150	Sewing
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, Wash Room
200-750	20-75	Conference, Reception Room	300-750	30-75	Cooking Room, Dining Table
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	50-75	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, Warehouse
300-500	30-50	Display Stand	150-200	15-20	Waiting Room
500-750	50-75	Elevator	200-750	20-75	Medical Exam Room
750-1,500	75-150	Show Window, Packing Table	750-1,500	75-150	Operating Room
1,500-3,000	150-300	Storefront, Show Window	5,000-10,000	500-1000	Eye Inspection

Two-year Warranty

Teledyne FLIR warrants this Extech brand instrument to be free of defects in parts and workmanship for two years from date of shipment (a six-month limited warranty applies to sensors and cables). To view the full warranty text please visit: http://www.extech.com/support/warranties.

Calibration and Repair Services

Teledyne FLIR offers calibration and repair services for the Extech brand products we sell. We offer NIST traceable calibration for most of our products. Contact us for information on calibration and repair availability, refer to the contact information below. Annual calibrations should be performed to verify meter performance and accuracy. Product specifications are subject to change without notice. Please visit our website for the most up-to-date product information: www.extech.com.

Contact Customer Support

Customer Support Telephone List: https://support.flir.com/contact

Calibration, Repair, and Returns: repair@extech.com

Technical Support: https://support.flir.com

www.extech.com

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