Extech Instruments 401025 User Manual page 3

Range Display Multipliers
Range Units
200 Fc
2000 Fc & Lux
5000 Fc
20,000 Lux
50,000 Lux
Using the range and unit selector switches. The switch on the left selects the range. The switch on
the right selects the unit. Note the factor of 10 and 100 in the higher ranges. For example, if a
measurement in the 5000 Fc range displays 350, the actual measurement is: 350 x 10 = 3500 Fc.
Measurement Range Considerations
The meter has three measurement ranges for each unit of measure (0-200, 0-2000, and 0-5000 Fc)
and (0-2000, 0-20000, and 0-50000) Lux). Selecting the correct range will provide the highest
accuracy. Always select the range that produces the maximum number of digits without exceeding
the range. For example, a reading of 1456 Fc should be read in the 2000 Fc range, not the 5000 Fc
range.
Zero procedure
To zero the display, follow the steps below. The display may drift due to temperature changes and
battery draining, so zero the display often.
1. Set the range switch to the lowest Lux or Fc range.
2. Completely cover the sensor to ensure that no light reaches it.
3. With the sensor covered, use a small screwdriver to adjust the zero screw to set a zero reading.
4. The right-most digit may fluctuate slightly. This is normal and does not affect the accuracy.
Analog Output
The analog output jacks on the front panel produce a 0.1 mV DC per digit signal that can be used for
recording and datalogging purposes. The maximum output is 200 mV DC.
Lighting Type Correction Factors
The meter is calibrated using a precise standard tungsten light source of 2856
used to measure a different type of light, refer to the correction factor table, below. Multiply the
reading by the factor, shown in the table for the specific light type.
Mercury
Fluorescent
Daylight
Sodium
Metal Halide
Multiplier
Direct reading
Direct reading
Reading x10
Reading x10
Reading x100
x 1.14
x 0.92 to 1.12
x 1.00
x 1.22
x 1.00
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K. If the meter is to be
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