Extech Instruments DT40M User manual

USER MANUAL
Laser Distance Meter
MODELS DT40M, DT60M, and DT100M

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Contents
Introduction ..........................................................................................3
Safety Instructions .................................................................................3
Descriptions...........................................................................................4
Measurement Preparation ......................................................................6
Programming Menu ...............................................................................8
Distance Measurements .........................................................................8
Area Measurements .............................................................................10
Volume Measurements.........................................................................12
Indirect Measurements (Pythagorean) ...................................................13
Stakeout Function ................................................................................16
20-point Datalogger .............................................................................17
Maintenance .......................................................................................18
Display Error Codes ..............................................................................20
Specifications.......................................................................................20

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Introduction
Thank you for selecting the Extech Laser Distance Meter. This meter
measures distance up to 40m (131.2’) for DT40M, 60m (197’) for
DT60M, or 100m (328.1’) for DT100M and calculates Area, Volume,
and Indirect readings using the Pythagorean Theorem (a2+b2=c2). It
also includes a laser pointer and a stakeout feature. Please visit
www.extech.com for the latest version of this User Guide, Product
Updates, and Customer Support.
Safety Instructions
This meter has been designed for safe use, but must
be operated with caution.
Laser classification (Class 2)
The meter produces a visible Class 2 laser beam from
the top of the instrument.
WARNING: Do not directly view or point the laser at an eye. Do not
look directly into the beam using an optical aid such as binoculars. This
can create a hazard. Low power visible lasers do not normally present a
hazard, but may present some potential for hazard if viewed directly for
extended periods of time.
Please read all safety instructions carefully before using this
instrument
Do not use this device in flammable or explosive environments
Do not use this device near aircraft or medical equipment
Do not use this device near strong electro-magnetic interference
Do not aim the meter directly into sunlight
Do not dis-assemble or modify the instrument
Do not store in areas of high temperature/humidity
Remove the batteries when storing the instrument for long periods

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Descriptions
Meter
1. LCD display area
2. Keypad
3. Level
4. Laser Pointer
5. Sensor Beam
Note: Battery compartment on back of meter
Display Description
1. Length measurement mode
2. Battery status
3. Datalogger icon and memory location (1~20)
4. Signal strength icons
5. Laser pointer default
mode
6. Edge Reference (from top
or bottom of meter)
7. Indirect measurements:
Single Pythagorean,
Double Pythagorean, and
Double Pythagorean
(partial height)
8. Stakeout mode
9. Area/Volume mode
10. Primary/summary display line
11. Auxiliary Display lines 1 (top), 2, and 3
12. Units of measure

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Keypad Description
Short press: Power ON
Short press: Laser ON (can be set to default ON)
Short press: Single distance measurement
Long press: Continuous measurement mode
Short press: Datalogger mode (press CLR to exit)
Long press: Open program menu
Short press: Clear display; Long press: Power OFF
Short press: Area/Volume mode
Long press to 1st beep: Stakeout mode
Indirect measurements
Press 1x: Single Pythagorean mode
Press 2x: Double Pythagorean mode
Press 3x: Double Pythagorean (partial height)
Add / Subtract keys
Short press: Measurement edge selection
Long press: Backlight ON/OFF
Short press: Select unit of measure

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Measurement Preparation
Measurement Considerations
1. For best results, choose a target that is flat, hard and smooth
2. Use a section of cardboard or similar material if the target
size needs to be increased
3. For distance measurements, this device performs best
indoors. If used outdoors, the range will be limited
depending on intensity of light and other environmental
factors.
4. Replace the battery if the battery icon flashes on the display
5. The meter will not measure through glass, liquid, or
Styrofoam
6. Inaccurate measurements may result from low battery,
measured distance exceeding specified range, and irregular
shaped objects near the target.
Range considerations
The range is limited to 40m (131.2’), 60m (197’), or 100m
(328.1’) depending on model. At night or dusk, if the target is in
shadow, the measuring range without target plate is increased.
Use a target plate to increase the range during daylight or if the
target has poor reflection properties. In unfavorable conditions
such as intense sunlight, poor reflective surfaces, or high
temperatures, distance readings over 10m (33’) can increase by
±0.15mm/m (±0.0018in/ft.).
Target surfaces
Measurement errors can occur when measuring toward colorless
liquids (e.g. water), dust free glass, Styrofoam or similar semi-

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permeable surfaces. Aiming at high gloss surfaces may deflect
the laser beam and lead to measurement errors. For non-
reflective and dark surfaces, the measuring time may increase.
Preparing for Measurements
1. Press the MEAS key to switch the meter ON.
2. You can elect either to have the Laser always ON or to have
the laser turn ON only when the MEAS key is pressed. Go to
the Programming Menu section of this manual for details.
3. The unit automatically switches OFF after three (3) minutes
of inactivity. Long press CLR to switch the unit OFF manually.
4. Press CLR to cancel the last action performed or clear the last
data displayed on the screen.
5. Press UNIT to change the unit of measure (ft = feet, in =
inches, m = meters.
6. Long press to turn the backlight on or off.
7. Short press the reference key to select the top edge or
bottom edge reference. See diagram below.
In the Top mode (2), the displayed reading will represent
the distance from the top of the meter to the target.
In the Bottom mode (1), the
displayed reading will
represent the distance from
the bottom of the meter to
the target. This is the
default mode.

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Programming Menu
1. Long press to open the programming menu
2. Use the MEAS button to step through the options
3. Use the (+) and (-) keys to make changes
4. Use the MEAS button to exit the menu
5. See table below for the program options
1
ON: OFF:
For distance measurements: Set Laser to
default ON/OFF. Use + key to select.
2
For all other measurements: Set Laser to
default ON/OFF. Use + key to select.
3
CAL. 0
Use +/- keys to offset display by ±7mm
4
bP. on/oFF
Use +/- keys to set beeper default ON/OFF
5
bL. On/oFF
Use +/-keys to set backlight default
ON/OFF
6
od. On/oFF
Unused mode
Distance Measurements
Single Distance Measurements
1. Momentarily press the MEASURE key to switch the meter ON;
Dashes (- - -) will appear on the display.
2. If the Laser point is already ON, go directly to step 3 below. If
the Laser point is not ON, press MEASURE to switch it ON.
3. Aim the meter and short press MEASURE to take a reading.
4. You can elect either to have the Laser always ON or to turn ON
only when MEASURE is pressed. Go to the Programming Menu
section of this manual for details.

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5. The reading will remain on the display until it is cleared with
the CLR key (short press) or until the meter is powered OFF.
Continuous Distance Measurements (with MAX-MIN)
This mode of operation is useful for determining the shortest
and longest distances from a given point. The meter can be
moved to various targets while the primary display (bottom)
updates with each new measurement. The MIN and MAX values
are displayed dynamically in auxiliary displays above the primary
display.
1. Press the MEASURE key to switch the meter ON.
2. Press and hold MEASURE for 3 seconds to begin a continuous
measurement session. The laser pointer will stay ON in
continuous mode.
3. The meter will beep with each new automatic measurement
update (approx. every one half second).
4. The MIN reading will be indicated (example below, left) and
will update each time a lower reading (< displayed MIN
reading) is encountered.
5. The MAX reading (example below, right) will be indicated and
will update each time a higher reading is encountered.
6. The actual reading will be indicated on the primary display.

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7. To stop measuring, short press MEASURE. Use the CLR key to
delete measurement displays.
8. Note that the meter exits to the normal mode of operation
after approx. 100 measurements in continuous mode.
Adding / Subtracting Distance Measurements
To display the sum or difference of two distance measurements:
1. Press the MEASURE key to switch the meter ON. Press
MEASURE to turn Laser ON, if it is not already ON.
2. Press MEASURE to take the first reading. The reading appears
on the primary display line (bottom).
3. Press the plus (+) or minus (-) key. The first reading will move
to auxiliary display line 2.
4. The plus or minus sign will appear on auxiliary display line 3.
5. Press MEASURE to turn Laser ON, if it is not already ON.
6. Press MEASURE to take the second reading. The second
reading appears on auxiliary display line 3.
7. Read the sum or difference of the two readings on the
primary display line.
8. Press CLR to cancel the last step or press MEASURE to move
the result (now shown in the primary display) to auxiliary
display line 2, for additional adding/subtracting work.
9. Press CLR to exit this mode or turn the meter OFF.
Area Measurements
Area Calculations
Computing the area of a room:
1. Press the MEASURE key to turn the meter ON.

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2. Press the key firmly once.
3. A parallelogram will appear with its length side flashing
indicating that a Length measurement is to be taken.
4. Press MEASURE to turn Laser ON, if it is not already ON.
5. Aim the meter and press MEASURE to take the room length
measurement.
6. The parallelogram will now appear with its Width side
flashing indicating that a Width measurement is to
be taken.
7. Press MEASURE to turn Laser ON, if it is not already ON.
8. Press MEASURE to take the room width measurement.
9. Auxiliary display lines 1 and 2 will now show the Length and
Width. The primary display will show the Area (in ft2or m2).
Note that the laser pointer will switch off automatically if too
much time is taken between steps. Press MEASURE to switch the
Laser pointer back ON and then try the test again.
Adding/Subtracting Area Calculations
1. After completing an Area calculation (see previous section),
with the resulsts displayed , short press the (+) key for the
‘summing’ mode or the (-) key for the ‘difference’ mode.
2. Perform another Area calculation as explained in the previous
section.
3. Press MEASURE and the display will show the change
(increased or decreased Area) from the first to the second
Area calculation in the primary display line (bottom).

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Auxiliary displays will show the two individual Area
calculations.
Volume Measurements
Volume Calculations
Compute room Volume:
1. Press the MEASURE key to switch the meter ON.
2. Press the key firmly twice.
3. A cube shape will appear with its Length flashing
indicating that a Length measurement is to be taken.
4. Press MEASURE to turn Laser ON, if it is not already ON.
5. Press MEASURE to take the room Length measurement.
6. The cube’s Width will now be flashing indicating that a
Width measurement is to be taken.
7. Press MEASURE to turn Laser ON, if it is not already ON.
8. Press MEASURE again to take the room Width
measurement.
9. The cube’s Height side will now be flashing indicating that a
Height measurement is to be taken.
10. Press MEASURE to turn Laser ON, if it is not already ON.
11. Press MEASURE to take the room Height measurement .
12. Auxiliary display lines 1, 2, and 3 will now show the Length,
Width, and Height respectively. The primary display
(bottom) shows the Volume in cubic feet or meters (ft3 or
m3).

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Adding/Subtracting Volume Calculations
1. After completing a Volume calculation (see previous section),
with the resulsts displayed , short press the (+) key for the
‘summing’ mode or the (-) key for the ‘difference’ mode.
2. Perform another Volume calculation as explained in the
previous section.
3. Press MEASURE and the display will show the change
(increased or decreased Volume) from the first to the second
Volume calculation in the primary display line (bottom).
Auxiliary displays will show the two individual Volume
calculations.
Indirect Measurements (Pythagorean)
Single Pythagorean Calculation (2 Measurements)
This device can measure the vertical height
from Point 1 to Point 2 with the operator
taking two measurements (Point X to 1 and
then Point X to 2).
1. Press the MEASURE key to switch the
meter ON.
2. Press once.
3. A right triangle shape will appear with its diagonal line
flashing.
4. Press MEASURE to turn Laser ON, if it is not already ON.
5. From exactly Point X, aim the instrument at Point 1 and
press MEASURE. One reading is now complete and the
bottom line of the right triangle will begin flashing.

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6. Press MEASURE to turn Laser ON, if it is not already ON.
7. From Point X, align the meter as horizontal as possible and
aim for Point 2 and then press MEASURE.
8. The measurements are now complete. The primary display
line (bottom) indicates the vertical distance from Point 1 to
Point 2. Auxiliary lines 1 and 2 show the two separate
measurements.
Double Pythagorean Calculation (3 Measurements)
This device can measure height in two
segments by taking three measurements. The
operator stands at Point X. The first
measurement is Point X to 1, the second
measurement is a horizontal line from Point X
to 2, and the third measurement is from Point
X to 3.
1. Press the MEASURE key to switch the meter ON.
2. Press the key two times.
3. The double triangle icon will appear with its top diagonal
line flashing.
4. Press MEASURE to turn Laser ON, if it is not already ON.
5. From Point X, aim the instrument at Point 1 and press
MEASURE. One reading is now complete and the middle line
of the double triangle will begin flashing.
6. Press MEASURE to turn Laser ON, if it is not already ON.
7. From Point X, aim the instrument horizontally at a Point 2
and press MEASURE. The second reading is now complete

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and the bottom diagonal line of the double triangle will begin
flashing.
8. Press MEASURE to turn Laser ON, if it is not already ON.
9. From Point X, aim the instrument at Point 3 and press
MEASURE. The third measurement is now complete.
10. The distance from Point 1 to Point 3 will now be indicated on
the bottom primary display line. Auxiliary display lines 1, 2,
and 3 will show the individual measurements.
Double Pythgorean Calculation (Partial Height)
This device can measure height from
Point 1 to Point 2 by taking three
measurements. The first measurement
is Point X to 1, the second
measurement is from Point X to 2, and
the third measurement is a horizontal
line from Point X to 3.
1. Press three times and the icon will display.
2. Press MEASURE to turn Laser ON, if it is not already ON.
3. Press MEASURE to measure from Point X to Point 1.
4. Press MEASURE to turn Laser ON, if it is not already ON.
5. Press MEASURE to measure from Point X to Point 2.
6. Press MEASURE to turn Laser ON, if it is not already ON.
7. Press MEASURE to take a measurement from Point X to
Point 3.
8. The measurement values for the three sides are shown in
the first, second, and third auxiliary displays. If the
measurement result conforms to the requirements of the

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Pythagorean Theorem, the calculated height will be
displayed in the primary display (bottom); otherwise an
error message will appear.
Notes: Ensure that the measurements are made from the same
point. Ensure that the right-angle measurement is made
perpendicular to the measured surface.
Stakeout Function
The stakeout function allows you to set up two separate distances
(Aand Bin diagram below) that can be used independently to
mark defined measured lengths (for example, in wood frame
construction or fence posting).
1. Press MEASURE to switch
the meter ON. Set the
measurement reference
to front or rear meter
edge using the key.
2. Press and hold until
the first beep.
3. On auxiliary display line 1, one digit for value “A” will flash.
Set the value of the "A" stakeout distance using the + and -
keys to change the value of a digit and MEASURE to move
from digit to digit.
4. Once the desired value has been set, press to move to
“B”on auxiliary display line 2.

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5. The “B” value will now flash. Use the + and –keys to adjust a
digit and the MEASURE key to move from digit to digit.
6. Once the desired value for “B” has been set, press to
start measuring and marking.
7. The third auxiliary display line shows the nearest stakeout
point. The primary display (bottom) shows the distance the
meter is from the nearest stakeout point.
8. Place the meter in position. When the meter is moved slowly
along the stakeout line, the primary display (bottom) will
decrease or increase (displaying a positive number [no sign]
when the measured distance is > the stakeout distance or a
negative number [- sign] when the measured distance is <
the stakeout distance).
9. The meter will start beeping at a distance of 0.1m (3.9”) from
the matching dimension. Note that the beep tone is different
for negative and positive values. The beeping tone will
change when you reach the stakeout distance.
10. Mark your locations accordingly.
11. Stop the measurement by pressing MEASURE.
20-point Datalogger
This device stores up to twenty (20) readings in memory.
1. Take a reading as previously described. The reading will
automatically be stored in memory location 20.
2. Take another reading, the reading that was stored in memory
location 20, previously, will move down to location 19 and the
new reading will be stored in location 20.

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3. To view stored readings, press to enter the datalogger
mode and use +/- keys to scroll. The memory location number
appears at the top of the LCD and the readings appear in the
usual primary and auxiliary display lines.
4. When scrolling through readings, note that the beeper tone is
different for ‘top’ edge reference readings and ‘bottom’ edge
reference readings.
5. When all twenty locations have been filled the meter begins
overwriting the existing readings (starting at location 20)
6. Press the CLR key to exit this mode.
Maintenance
WARNING: Do not operate the meter until the battery
compartment cover is in place and fastened securely.
This instrument is designed to provide years of dependable
service, if the following care instructions are performed:
1. Keep the meter dry and free from dust.
2. Use and store the meter in nominal temperature conditions.
Temperature extremes can shorten the life of the electronic
parts and distort or melt plastic parts.
3. Handle the meter carefully and avoid shock and vibration.
Dropping the meter may damage the electronic parts or the
case. Handle as you would a camera or telescope.
Cleaning
1. Do not immerse the instrument in water.
2. Wipe the case occasionally with a damp cloth. DO NOT use
chemicals, cleaning solvents, abrasives, or detergents. Clean

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and maintain the instrument lenses in the same manner as
for professional camera lenses with high quality lens wipes.
Battery Installation/Replacement
When the low battery symbol appears on the display or when
the display does not switch ON, replace the batteries.
1. Power OFF before replacing the batteries.
2. Open the rear battery compartment.
3. Replace the two (2) ‘AAA’batteries observing correct polarity.
4. Replace the battery compartment cover.
Battery Safety
Use only fresh batteries of the correct type. Remove old or weak
batteries so they do not leak and damage the unit.
If the meter is to be stored for long periods, the batteries should be
stored separately to prevent damage to the unit.
Never dispose of batteries in a fire. Batteries may explode or leak.
Never mix battery types. Always install new batteries of the same
type.
Never dispose of used batteries or rechargeable batteries in
household waste.
As consumers, users are legally required to take used
batteries to appropriate collection sites, the retail store where
the batteries were purchased, or wherever batteries are sold.
Disposal: Do not dispose of this instrument in household waste. The
user is obligated to take end-of-life devices to a designated collection
point for the disposal of electrical and electronic equipment.

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Display Error Codes
For any error, cycle power to see if the error clears. If the error
persists after several power cycles, refer to the information below.
Display
Reason
Action required
Calculation error
Re-test
Weak signal reception
Measurement time-out
Use target plate
Hardware failure
Return for service
Specifications
General Specifications
Display
5-digit (99999) backlit, multifunction LCD
Laser diode
Class 2 red laser (wavelength: 635nm)
Battery
Two (2) ‘AAA’ alkaline batteries
Battery Life
5,000 measurements (approx.)
Backlight APO
After 35 seconds
Laser APO
After 35 seconds
Meter APO
After 3 minutes
Operating conditions
0 to 40°C (32 to 104°F)
Storage conditions
-20 to 60°C (-4 to 140°F)
Dimensions
116 x 56 x 32mm (4.6 x 2.2 x 1.3”)
Weight
100g (3.5 oz.)