USER GUIDE LED Light Meter Model LT45
Introduction Congratulations on your purchase of the Extech LT45 LED Light Meter that measures light from LED lamps in addition to fluorescent, metal halide, high‐pressure sodium and incandescent sources. The LT45 is capable of measuring the illumination of white, red, yellow, green, blue, and purple LEDs up to 400,000 Lux (40,000 Fc). The LT45 can also calculate luminous intensity (CD) using a distance‐to‐the‐light value programmed by the user in meters or feet units.
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 battery symbol Do not touch the meter’s circuit board for any reason as 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 2000m (7000’). appears on the LCD.
Operation Power ON‐OFF Momentarily press the Power button to power the meter. To power the meter OFF, momentarily press the Power button again. Taking Measurements 1. Switch the meter ON 2. Remove the sensor’s protective cover to expose the light sensor dome. The display should switch ON, if not check that fresh batteries are installed. 3. The meter measures the intensity of the light (illuminance) that strikes the sensor dome in foot candles and lux units (1 fc = 10.
MAX/AVG/MIN Memory Mode The meter can record the maximum, minimum, and average readings as described below: button and the meter will begin to track the 1. Momentarily press the MAX/AVG/MIN maximum/average/minimum measurements; the “MIN” icon will display on the LCD indicating that the meter is now displaying the minimum reading. The reading will not change until a lower reading is registered. button again to switch from “MIN” to “MAX” where the meter will show the 2. Press the maximum measurement value.
Luminous Intensity (CD) Measurements 1. Press the On/Off button to turn power ON. 2. Press and hold the LX/FC/CD button until the meter’s unit designator switches to CD. 3. Use the arrow buttons to select ft (feet) or m (meter) units to represent the distance the sensor will be from the light source. 4. Momentarily press the LX/FC/CD button; the smaller digits (lower‐right hand corner of LCD) will switch ON, these digits represent the distance to the light source. 5.
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, covering the light sensor. This will prolong the life of the sensor. When the meter is to be stored for long periods, please remove the battery and store it separately. Batteries can leak and cause damage to the meter’s components.
Specifications Sampling rate 2.5 times per second (digital display) Display 6‐digit LCD with 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, *39999, *399999 Foot‐candles: 39.99, 399.9, 3999, *39999 *Above 3999, the LCD uses smaller digits on the right side (1 Fc = 10.
Appendix Typical Light Levels Lux Foot Candles 20‐75 75‐150 2‐7 7‐15 150‐300 15‐30 300‐750 750‐1,500 1,500‐3,000 30‐75 75‐150 150‐300 75‐100 100‐200 7‐10 10‐20 200‐750 20‐75 750‐1,500 1,500‐2,000 75‐150 150‐200 200‐300 Lux Foot Candles Factories Emergency Stairs, Warehouse Exit/Entrance Passages 100‐150 150‐200 10‐15 15‐20 Packing Work 200‐300 20‐30 300‐500 500‐1,500 1,000‐2,000 30‐50 50‐150 100‐200 75‐150 150‐300 7‐15 15‐30 300‐750 30‐75 750‐1,500 75‐150 30‐75 75‐100 100‐150 3
