Operation; Taking Measurements; Zero Calibration - Extech Instruments LT45 User Manual

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 = 10.76 lux) displaying the measured value on the LCD.
4. Use the LUX/FC/CD button to select Lux or Foot candle units (CD, luminous intensity, is
explained in the dedicated section 'Luminous Intensity'). When 'OL' is displayed, the
measurement exceeds the meter's range capability.
5. Position the meter and light source so that the light strikes the sensor dome perpendicularly.
Although the meter compensates for an incidence angle, optimum performance is achieved
with a smaller incidence angle.
6. The meter's LCD can show a value up to 3999 on the large digits and when more digits are
needed to represent the reading two additional (smaller) digits appear to the right of the
larger digits, e.g. 3999
LUX/FC/CD Units
Momentary presses of the LUX/FC/CD button toggles Lux and FC (foot‐candles) units. Press and
hold the button to enter the CD (luminous intensity) mode. Refer to 'Luminous Intensity' section
for further information.
Auto Power OFF
To save battery life the meter powers down automatically after approximately 5 minutes of
inactivity (no button presses).
Enable/Disable Auto Power Off
With the meter ON, press and hold the Power button until the APO clock symbol
OFF (the Auto Power OFF utility is now disabled and the user must manually switch the meter
off). To re‐enable the Auto Power OFF utility, repeat this process. The Clock symbol will switch
ON when the Auto Power OFF utility is re‐enabled.
Zero Calibration
1. Ensure that the protective cover is attached to the light sensor.
2. Power the meter and the LCD should display '0'.
3. Momenarily press the "ZERO" button and the ADJ (adjusting) icon will switch ON indicating
that the zero adjustment (calibration) is working. When the calibration is finished, the ADJ
icon will switch OFF and the meter will return to the normal operating mode.
4. 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.
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