Extech Instruments MO257 User manual

User's Guide
Pinless Moisture Meter
Model MO257

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Introduction
Congratulations on your purchase of the Extech MO257 Pinless Moisture Meter. The pinless
moisture sensor monitors the moisture in wood and other building materials without causing surface
damage. High frequency sensing technology allows the meter to take non-invasive moisture
measurements. User programmable alarms alert the user if moisture measurements exceed alarm
set-points. This meter is shipped fully tested and calibrated and, with proper use, will provide years of
reliable service.
Meter Description
1. Measurement sensor
2. Power ON-OFF button
3. LCD display
4. Measure (MEAS) button
5. UP and BACKLIGHT button
6. SET button
7. DOWN button
Battery compartment located on rear of unit
LCD Display
1. Low Battery icon
2. Main LCD display
3. MAX reading
4. MIN reading
5. HOLD function
6. Measurement alert
7. MAX mode icon
8. MIN mode icon

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Battery Replacement
1. Turn off the meter
2. Remove the Philips head screw located on the rear of the unit
3. Lift off the rear battery cover
4. Replace the three (3) ‘AAA’ 1.5V batteries
5. Secure the rear battery cover
You, as the end user, are legally bound (EU Battery ordinance) to return all used
batteries, disposal in the household garbage is prohibited! You can hand over your
used batteries / accumulators at collection points in your community or wherever batteries
/ accumulators are sold!
Disposal: Follow the valid legal stipulations in respect of the disposal of the device at the
end of its lifecycle

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Operation
Pinless Moisture Measurements
1. Press the power button to turn the meter on.
2. As described below, you must calibrate the meter before first use.
3. To calibrate, press the MEAS button immediately after powering on the meter. The display will
audibly beep and visually flash the CAL display icon. Keep the measurement sensor at least 3
to 4” (8 to 10 cm) from any object during calibration.
4. When the calibration is complete the beeping and flashing stop. The calibration reading must
not exceed 0.5. If so, re-calibrate ensuring that hands or other objects are kept clear of the

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Auto Power Off
To conserve battery energy, the meter will enter a sleep mode after approx. 30 minutes of inactivity.
Press the power button to wake the meter.
Backlit LCD
Press the up/backlight button to switch the backlighting ON or OFF.
Specifications
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Moisture Range 0.0 to 100.0 Relative only
Measurement Depth 20 to 40mm (0.79 to 1.57”)
Display type Backlit LCD
Display digits Three (3) numeric displays; each displaying from 0.0 to 100.0
Display icons HOLD, DRY, RISK, WET, MIN, MAX and low battery icon
Operating Temperature 4 to 43°C (40 to 110°F)
Operating Humidity 90%, 0-30°C (32-86°F), 75%, 30-40°C (86-104°F),
45%, 40-50°C (104-122°F)
Power Supply Three (3) 1.5V ‘AAA’ batteries
Auto Power Off (APO) After 30 minutes of inactivity
Dimensions 235 x 63 x 28mm (9.2 x 2.5 x 1.1”)
Weight 218g (7.7oz)
Moisture Comparison Table (typical)
Material Display units Moisture status
< 30 DRY
30 - 60 RISK
Gypsum
> 60 WET
< 25 DRY
25 - 50 RISK
Cement
> 50 WET
< 50 DRY
50 - 80 RISK
Wood
> 80 WET
©2012 Extech Instruments Corporation (a FLIR company)
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Phone: [phone]
E-mail: [e-mail]
web: www.airconcern.co.uk
Air Concern Ltd, Building 173 Curie Avenue Harwell Didcot, Oxfordshire OX11 0QG
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