General DLM204 User manual
WIDE RANGE
SINGLE PIECE
DIGITAL LIGHT METER
USER’S MANUAL
DLM204
Please read this manual carefully and thoroughly before using this product.
TABLE OF CONTENTS
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 –3
Key Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 –4
Safety Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
What’s in the Package . . . . . . . . . . . . . . . . . . . . . . . . 4
Product Overview . . . . . . . . . . . . . . . . . . . . . . . . . 4 –5
Setup Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Install Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Operating Instructions . . . . . . . . . . . . . . . . . . . . . 6 –9
Choosing the ight ange . . . . . . . . . . . . . . 6 –8
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . 9 – 10
Operating & Maintenance Tips . . . . . . . . . . . . . . . . 10
Warranty Information . . . . . . . . . . . . . . . . . . . . . . . . 11
eturn for epair Policy . . . . . . . . . . . . . . . . . . . . . . 12
INT ODUCTION
Thank you for purchasing General Tools & Instruments’
DLM204 Wide Range Single Piece Digital Light Meter. Please
read this user’s manual carefully and thoroughly before using
the instrument.
The DLM204 is a general-purpose handheld instrument
suitable for measuring the intensity of visible light in
commercial, industrial, and consumer settings such as
offices, factories, hospitals and schools. Applications include
compliance with safe lighting regulations, facilities
management, security, photography, videography,
engineering, construction and surveillance.
2
The meter displays measured light intensity in either of two
units: lux and foot-candles. The lux is the standard
international unit of illuminance, or how much luminous flux
is spread over a given area. One can think of luminous flux as
a measure of the total amount of visible light present, and
illuminance as a measure of the intensity of illumination on a
surface. A given amount of light will illuminate a surface more
dimly if it is spread over a larger area, so illuminance is
inversely proportional to area.
The standard international unit of luminous flux is the lumen,
and one lux is equal to one lumen/m2. or perspective on lux
readings from the natural world, a moonless clear night sky
has an illuminance of about 0.002 lux, while direct sunlight
has an illuminance of 30,000 to 130,000 lux.
The foot-candle (or lumen per square foot) is a non-standard
unit of illuminance. Like the Btu, it is mainly in common use
only in the U.S., particularly in construction-related
engineering and building codes.
Lux and foot-candles are different units of the same quantity.
One foot-candle (ft-cd) = 10.764 lux, and 1 lux = 0.0929 ft-cd.
The DLM204 has a 2 in. diagonal LCD with 1 in. high digits.
The meter is powered by a “9V” battery (included in the
package).
KEY FEATU ES
• Readings displayed in lux or foot-candles
• Choice of four ranges for each unit
• Large 2000 count LCD
• Uses cosine angular correction, silicon photodiode and
filter to approximate relative spectral response curve
3
used by the International Illumination Commission (CIE)
and adopted by Japanese Industrial Standard C
1609:1993
• Zero adjustment • Max memory + data hold
• Low battery and overload indications
• One-handed operation • CE and RoHS approved
• 1-year limited warranty
SAFETY INST UCSSTIONS
Do not operate the DLM204 in the presence of combustible
gases or combustible materials (including dust in high
concentration).
WHAT’S IN THE PACKAGE
The DLM204 is packaged in a white box along with a soft
pouch, a “9V” battery and this user’s manual
P ODUCT OVE VIEW
The figure at right shows all
controls, indicators and
physical features on the front,
back and right side of the
DLM204. amiliarize yourself
with their positions and
functions before moving
on to the Setup
Instructions.
The DLM204’s controls,
indicators and physical
features
4
쐅
1. LCD 2. (power) button 3. M-H button
4. Lx/Fc button 5. D-H button 6. button
7. Light sensor with cap 8. 0 ADJ hole (on right side)
9. Tripod mount (on back)
10. Battery compartment (on back)
SETUP INST UCTIONS
INSTALL BATTERY
The DLM204’s battery compartment is under a cover on the
lower back of the unit (Callout 10 of the figure). To open the
compartment, turn the meter over and slide the cover down in
the direction of the OPEN arrow.
Plug the included “9V” battery into the wired socket inside the
compartment. The terminals of the battery and the socket
mate in only one way, with the smaller male terminal
plugging into the larger female terminal.
Position the battery and socket in the compartment so the
socket’s wires run under the battery, rather than above it.
To close the battery compartment:
1) Cradle the meter face-down in your “off” (weaker) hand.
2) With your other hand, position the cover above the battery
so its flanged top edge is touching the top edge of the
compartment.
3) Place the tip of your index finger on the cover’s ribbed area
marked OPEN and the tip of your thumb near the cover’s
curved, bottom edge.
4) Push both ends of the cover down and forward until it
snaps into place.
5
OPE ATING INST UCTIONS
To power the meter on or off, press the green button.
Before making any measurements, remove the cap covering
the light sensor (Callout 7). Do not detach the cap from the
lanyard.
Begin by selecting a measurement unit—lux or foot-candles.
Pressing the Lx/Fc button (Callout 4) toggles between the two
units. When the DLM204 powers on, it automatically resumes
using the last unit selected. In other words, whichever
measurement unit you select becomes the meter’s default
unit until you change it.
To make an initial measurement, position the meter so the
light sensor is as close to perpendicular to the source of light
as possible.
If your reading is OL. or OL, there is enough light to overload
the meter using its current measurement range. You must
switch to a wider measurement range.
CHOOSING THE RIGHT RANGE
The DLM204 provides four manually selectable ranges for
each of the two measurement units: lux and foot-candles
( C). Repeated presses of the button (Callout 6) cycle
through the four ranges for each unit. The following two
graphics illustrate the sequence.
20 씰200 씰2000 씰20000 FC
and
200 씰2000 씰20000 씰200000 LUX
6
The measurement unit in use will determine which of the two
graphics appears at the bottom of the LCD, below the
measured light level. In each graphic, there will be a line
above or below one of the four values, indicating that it
represents the high end of the measurement range currently
in use. In the upper graphic at the bottom of the previous
page, the line above 2000 FC indicates that the currently
selected range is 0 to 2000 foot-candles. In the lower
graphic, the line below 2000 LUX indicates that the currently
selected range is 0 to 2000 lux.
Press the button and note that doing so moves the
overscore or underscore mark one step to the right, above the
next-widest range—unless the meter is already using the
widest range. In this case, pressing the button causes the
mark to “wrap around” to the narrowest range, on the left.
or any light-level value, the “right” measurement range is
not just the one that avoids an OL or OL. readout. It is also the
range that provides the reading with the highest resolution.
To illustrate this concept, measure a dim light—one that
produces a reading using the narrowest range of either
measurement unit. or example, say that your reading is
12.24 FC on the 0 to 20 FC scale (range). Press the button
to switch to the wider 0 to 200 FC range and note that the
readout changes to 12.2 FC. Then press the button again to
switch to the even-wider 0 to 2000 FC range. The readout will
change to 12 FC.
Clearly, the reading of 12.24 FC produced by using the
0 to 20 FC range provides the most precise (highest-
resolution) measurement among the three ranges used in this
example. Each of the eight available ranges has an inherent
measurement resolution—the smallest change in a reading
7
that it can resolve. On the DLM204, the 0 to 20 FC range has
the highest resolution because its readings are always
integers followed by two decimal places. The two ranges with
the next-best resolution are 0 to 200 FC and 0 to 200 LUX;
each can resolve measurements to one decimal place. The
other five available ranges have the worst resolution; none of
them can measure light levels with an accuracy of less than
1 lux or 1 foot-candle.
or the sake of accuracy, you should try to maximize the
resolution of every measurement that you make—by
switching to the next-narrowest range. If doing so produces a
reading with an additional decimal place, your effort will be
rewarded by a more-accurate reading. If switching to the
next-narrowest range produces an overload, simply return to
the previous range.
Whichever range you choose will automatically become the
default range used by the meter when it is powered up
following a shutdown. In other words, the DLM204
“remembers” both the measurement unit and the
measurement range in effect when it was last used.
To hold any reading (“freeze” the display), press the D-H
button (Callout 5). D-H will appear on the top line of the LCD.
This feature is useful for making measurements above your
head, below your knees, or around a corner. Held readings
can be viewed at eye level later.
To release the display and resume making real-time readings,
press the D-H button again.
The DLM204 can also keep track of the maximum light levels
measured during a measurement session—the period of time
that begins when the meter is powered on and ends when it
is powered off.
8
To display the maximum light level recorded during the
current measurement session, press the M-H button. Doing
so will cause the term MAX to appear on the top line of the
LCD, above the highest (maximum) value recorded.
To return to displaying real-time light-level readings, press
the M-H button again.
SPECIFICATIONS
Overall Measurement Range: 0 to 20,000 foot-candles
(ft-cd)/0 to 200,000 lux
Individual Ranges/Resolutions: 0 to 20 ft-cd/0.01 ft-cd;
0 to 200 ft-cd/0.1 ft-cd; 0 to 2,000 ft-cd/1 ft-cd; 0 to
20,000 ft-cd/10 ft-cd; 0 to 200 lux/0.1 lux; 0 to 2,000 lux/
1 lux; 0 to 20,000 lux/10 lux; 0 to 200,000 lux/100 lux
Measurement Accuracy: ±3% of reading for standard
incandescent lamp operating at 2856°K; ±6 to 8% for
other visible light sources (incandescent, fluorescent,
high-pressure sodium and metal-halide lamps)
Angular Deviations from Cosine Characteristics:
±2%@30°, ±6%@60°, ±25%@80°
Ranging Type: Manual only
Display Type & Size: 2 in. (50mm) diagonal LCD with 1 in.
(25mm) high digits
Display Resolution/Refresh Rate:
2000 counts/2.5 times/second
Light Sensor Type: Silicon photodiode
Environmental Classification: Pollution Degree 2
(offices, laboratories and test stations)
Operating Temperature:
14° to 122° (-10° to 50°C)@<80%RH
9
Operating Altitude: Up to 2000m (6561 ft.)
Storage Temperature: 14° to 122° (-10° to 50°C)@<70%RH
Dimensions: 6.7 x 2.2 x 1.5 in. (172 x 55 x 38mm)
Weight (including battery): 8.8 oz. (250g)
Power Source: (1) “9V” battery
(NEDA 1604/IEC 6 22/JIS 006P)
OPE ATING & MAINTENANCE TIPS
Keep the light sensor clean and covered by the protective cap
when the meter is not in use.
When the icon appears on the LCD, it’s time to replace
the “9V” battery that powers the meter (although
measurements will remain valid for several hours after the
low-battery indicator first appears). To replace the battery,
follow the instructions on page 5.
To avoid draining the battery prematurely, remember to
power off the meter after each measurement session. The
DLM204 has no Auto Power Off (APO) function.
Remove the battery before storing the meter for an extended
period of time (months rather than weeks), to minimize the
risk of having the battery leak and damage or ruin the meter.
Every so often, perform a rough calibration of the meter by:
1) Selecting the 0 to 20 FC range; and 2) placing the
protective cap over the light sensor with the meter on. If this
does not produce a reading of 0.00 FC, use the end of a
paper clip to press the 0 ADJ button on the right side of the
meter.
Try not to drop the meter. And never disassemble it or
immerse it in water; doing so would void the limited warranty.
10
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