USER GUIDE White LED Light Meter Model LT40
Introduction Congratulations on your purchase of the Extech LT40 LED Light Meter that measures light from white LED light, fluorescent, metal halide, high‐pressure sodium and incandescent sources. The LT40 can measure light up to 400,000 Lux (40,000 Fc). The LT40 offers an overload indication, low battery indication, Data hold, maximum/average/minimum hold (MAX/MIN), Zero adjustment, auto power off with disable function, and auto ranging features.
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. Calibration and ZERO button 3. Maximum/Average/Minimum memory button 4. Data hold button 3 LT40-EU-EN v1.
Operation Power ON‐OFF Press and hold the Power button for at least 2 seconds and then release to power the meter. To power the meter OFF, momentarily press the Power button. Taking Measurements 1. 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. 2. The meter measures the intensity of the light (illuminance) that strikes the sensor dome in foot candles and lux units (1 fc = 10.
MAX/MIN Button The meter can record the maximum, minimum, and average readings as described below: 1. Momentarily 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. 2.
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 Display 4‐digit LCD (maximum display: 3999) with low battery icon, measurement overload, and other function indicators Sensor (detector) Silicon photodiode with spectral response filter and cosine correction Ranges and Resolution Lux: 399.9, 3999, *39 999, *399 999 Foot‐candles: 39.99, 399.9, 3999, *39 999 * Readings above 3999 use a x10 or x100 multiplier (1 Fc = 10.
Appendices Typical Light Levels (1 Fc = 10.
