USER MANUAL White LED Light Meter Model LT40 Additional User Manual Translations available at www.extech.
Introduction Congratulations on your purchase of the Extech LT40 LED Light Meter that 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.
Meter Description 1. Photo detector (remove protective cover to expose sensor) 2. Display (LCD) 3. Control push‐buttons 4. Power Button: ON/OFF Battery compartment and tripod mount are located on rear of instrument Push‐Button Description 1. Lux/Fc units selector 2. Zero Calibration button 3. Maximum/Average/Minimum memory button 4. 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.
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 will switch OFF). To enable the Auto Power OFF utility, repeat this process. Clock symbol LUX/FC Button Press the LUX/FC button to toggle between Lux and FC (foot‐candles) measurement units.
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.
Specifications Units Lux Foot candles Range Resolution 999.9 0.1 9,999 99,990* 1 10 400,000* 100 99.99 999.9 0.01 0.1 9,999 40,000* 1 10 Accuracy White LED: ±(3%reading + 3 Lux) up to 500 Lux ±(3%reading) >500 Lux Other light sources: Unspecified White LED: ±(3%reading + 0.3 Fc) up to 46 Fc ±(3%reading) >46 Fc Other light sources: Unspecified * Readings above 9999 use a x10 or x100 multiplier Angle deviation from cosine characteristics (1 Fc = 10.
Appendices Typical Light Levels (1 Fc = 10.
