User Manual

and lowest reading is the effective light value.
Conversion factors are shown below for other units of measurement.
lux = footcandles x 10.8
footcandles = lux x .093
cd/m
2
(nit) = footlamberts x 3.43
footlamberts = cd/m
2
x .392
To determine candlepower (luminous intensity) of a light source, measure footcandles at a known distance
from the source. Preferably, the distance (d) should be 10 times (or more) greater than the size of the source.
Then multiply the square of the distance by footcandles to obtain candlepower in candela. candlepower =
ft.cd. x d
2
.
The amount of candela calculated above is the intensity of light emitted in the direction of the measurement
position. It is sometimes called beam candlepower.
Electric lamps are frequently specified in terms of lumens output. This figure is not so useful as beam
candlepower for predicting footcandles at the area of interest, since the beam pattern of the lamp is usually
not known. Also, lamp housings, reflectors, and lenses can have a great effect on beam candlepower. For
detailed definitions of the terms of light measurement you may consult the various books available, including
RCA's Electro-Optics Handbook, RCA, Harrison, N.J. 07029, especially Section 2.
7. BATTERIES
When the batteries are low the display will light a marker above the 2nd and 3rd display digits.
To change batteries, loosen the battery door screw with a coin. Handle the new batteries with tissue paper to
avoid corrosion of the contacts. Replace with type A-76 button cells, or alternate types MS-76, 10L14,
RW42, 357.
If the instrument will not operate, clean all batteries and contacts inside the instrument. Be careful to use a
clean cloth or paper. Observe battery polarity.
8. OPTIONAL ACCESSORIES
All optional adapters must be calibrated to the Photo-Meter with which they will be used. Therefore, when
ordering accessories the Photo-Meter must be returned to Quantum for re-calibration.
The appropriate accessories are listed in Section 1 with each model type. Costs and delivery time for
accessories may be obtained by contacting us:
Quantum Instruments Inc.
1075 Stewart Ave.
Garden City, NY 11530
Tel: [phone]
Fax: [phone]
Email: [e-mail]