Extech Instruments MW12 User manual

User Guide
Moisture Meter
Model MO250
99 Washington Street
Melrose, MA 02176
Phone [phone]
Toll Free 1-800-517-8431
Visit us at www.TestEquipmentDepot.com
Back to the Extech MO250Product Page
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX [phone] - TestEquipmentDepot.com

MO250 V2.1 6/06
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Introduction
Congratulations on your purchase of the Extech MO250 Moisture Meter. The MO250
detects moisture in wood and other building materials such as brick, wall board, sheet
rock, cardboard, paper, plaster, concrete, and mortar. This meter is shipped fully tested
and calibrated and, with proper use, will provide years of reliable service.
Features
•Designed to check the moisture level of wood, concrete, and other non-wood material
•Measures from 6% to 40% moisture in wood
•Measures 13% to 100% relative moisture for concrete and other non-wood material
•Measurements are shown on Red LED bargraph indicator and LCD digital display
•Optional external moisture sensor probe (MO252) for remote moisture measurements
•Microprocessor provides high accuracy and advanced features such as MAX / MIN
•Data Hold feature freezes displayed reading
•Heavy duty construction and compact housing enhance portability and durability
•Low battery indicator alerts user when battery needs replacing
Description
Meter Description
1. External probe input
2. Measurement electrode pins
3. LCD display
4. POWER key
5. HOLD key
6. REC MAX/MIN key
7. MATERIAL key
8. LED bargraph
9. External probe plug
10. External probe (Optional)
Notes:
•External probe is optional (use part number MO252 to order probe)
•Battery compartment, tilt stand, and tripod mount are located on the rear of the
instrument
•Electrode pin protective cover not shown
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX [phone] - TestEquipmentDepot.com

MO250 V2.1 6/06
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25.0
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36.9
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Operation
Electrode Pins
The electrode pins are replaceable / removeable and must be inserted before the meter
can be used. To insert or replace the pins refer to the illustration and instructions below:
a) Remove the protective cap at the top of the meter
b) To remove the pins, loosen the locknut at the base of the electrode pins
c) Install the new pins and tighten the locknuts
d) Replace the protective cap
1. Electrode pins
2. Locking nuts
3. Threaded posts
4. Electrode jacks at top of meter
Basic Operation
1. Remove the protective cap to expose the electrode pins.
2. Press the POWER key to turn the meter ON / OFF.
3. Press the MATERIAL key to select the material under test.
A ‘1’ will appear in the right bottom display for concrete and other non-wood
material. A ‘2’ will appear for wood. See details below:
Material 1: 13 to 100% relative moisture for concrete and other non-wood
materials; display shows a ‘1’ on the bottom right.
Material 2: 6% to 40% moisture range for wood; the display shows a ‘2’ on the
bottom right.
CAUTION: The electrode measurement pins are extremely sharp. Use care when
handling this instrument. Cover the pins with the protective cap when the
instrument is not in use.
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3
4
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Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX [phone] - TestEquipmentDepot.com

MO250 V2.1 6/06
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4. Carefully push the electrode pins a minimum of 0.07” (2mm) into the material under
test. Note that the pins should be
inserted into wood perpendicular
to the wood’s fiber structure. For
high moisture readings, it may
take several minutes for the
meter reading to stabilize.
5. Take several readings in several
locations on the material for the
best representation of the
amount of moisture present.
6. Read the measurement values
on the LCD digital display or the LED bar graph (see bargraph diagram)
7. Replace the protective cap when finished.
1. Material 1 (non-wood) moisture scale 13-100%
2. Material 2 (wood) moisture scale 6-40%
3. LED bargraph reading
4. Color code for material 2 (High Moisture)
5. Color code for material 2 (Medium Moisture)
6. Color code for material 2 (Low Moisture)
7. Color code for material 1 (High Moisture
when LEDs reach darker color)
Data Hold feature
The Data Hold function freezes the reading in the display. Press the HOLD key
momentarily to activate the Data Hold function. The reading will freezee and the ‘HOLD’
display icon will appear. Press the HOLD key again to exit the Data Hold function (the
HOLD display icon will switch off).
Max/Min Memory feature
The meter’s Max/Min feature allows the user to take multiple readings while storing the
highest (Max) and lowest (Min) readings.
1. Press the REC MAX/MIN key to activate the MAX/MIN recording mode. The
display icon ‘REC’ will appear. Now begin taking measurements.
2. To view the MAX reading, press the REC MAX/MIN key again. The display icon
‘MAX’ and the maximum recorded value will appear on the display. The meter will
now display and hold the maximum reading. To return back to the MAX/MIN
recording mode, press the ‘HOLD’ key. It will update only when a new ‘Max’
occurs.
3. To view the stored Min reading, press the REC MAX/MIN key again. The display
icon ‘REC MIN’ and the minimum value will appear on the display. The meter will
display and hold the minimum reading. To return back to the MAX/MIN recording
mode, press the HOLD key. It will update only when a new ‘Min’ occurs.
4. To exit MAX/MIN mode press and hold the REC MAX/MIN key for 2 seconds then
release. The display icon ‘REC’will switch off.
0.07” (2mm)
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX [phone] - TestEquipmentDepot.com

External Probe (optional)
An optional external probe is available (part number MO252) that allows the user to reach
into areas that would be difficult to access with the meter’s built-in electrode pins.
1. The input socket for the external probe is located at the top of the meter.
2. The plug and jack are keyed so that the plug can only fit in the jack one way.
3. Turn the plug carefully until it lines up with the jack and then firmly push the plug in
place. Do not apply undue force or try to twist the plug side-to-side.
4. The meter will continue to operate as described in this manual.
Battery Replacement
If the instrument does not switch ON or displays the low battery symbol , replace the
battery as follows:
1. Open the rear battery cover by removing the screw using a Phillips head
screwdriver
2. Replace the 9V battery
3. Put the battery cover back in place. Secure with the Phillips screw.
Maintenance
•Always keep the instrument dry
•To clean, wipe the meter with a damp cloth. Use a mild detergent if necessary
but never use abrasives or solvents.
•Prevent dirt from accumulating at the electrode pins
Specifications
Display LCD digital display and red LED bargraph scale
Resolution 0.1%
Accuracy ± (5% rdg + 5 digits)
Sampling rate One reading every 0.8 seconds (approx.)
Memory Maximum and Minimum readings can be saved and viewed
Measurement principle Electrical resistance
Range Wood: 6 to 40%, Building materials: 13 to 100%
Electrode pin length 0.44” (11mm)
Electrode pin type Integrated, replaceable
Power supply 9V alkaline battery
Power consumption 16mA DC (approx.)
Low Battery Indication Battery symbol displayed on LCD
Meter housing Impact-proof plastic
Operating Temperature 32 to 122oF (0 to 50oC)
Operating Humidity 80% Relative Humidity maximum
Dimensions 8.4 x 2.7 x 1.2” (216.5 x 68.5 x 29.7mm)
Weight 8.8 oz. (251g)
99 Washington Street
Melrose, MA 02176
Phone [phone]
Toll Free 1-800-517-8431
Visit us at www.TestEquipmentDepot.com
Back to the Extech MO250Product Page