Please read these instructions carefully and thoroughly before using the product.
INTRODUCTION
Thank you for purchasing General Tools & Instruments’ MM9
Combo Moisture Meter. Please read this user’s manual carefully
and thoroughly before using the instrument.
The MM9 is designed for use in woodworking, water damage
restoration, building construction and home renovation.
Examples include:
• Checking for moisture and mold on or below the surface of
carpets and subflooring
• Measuring the moisture content of wood, drywall or cement
board before painting, wallpapering, sealing or treating
• Locating water leaks above ceilings, below floors or behind
walls
• Selecting dry lumber
The MM9 can be operated in either of two modes. One is
pinless (non-invasive).
moisture up to 3/8 in. below the surface of drywall, 1/4 in. below
the surface of cement board, and 3/4 in. below the surface of
wood without marring the material with pinholes. It infers the
level of moisture from the material’s capacitance, which the
meter measures by gauging its effect on an electric field that the
meter generates each time it is powered on.
In this mode, the meter can detect
The meter exploits two physical phenomena to make its pinless
measurements:
1. The linear relationship between a solid material’s moisture
level and its dielectric constant—and therefore its
capacitance.
2. The so-called fringing-field effect—the slight spreading of the
electric field produced by current flowing between two
electrodes when both electrodes are on the same side of a
material.
Behind the top of the MM9 are two metal plates. When the meter
is powered on, the plates are given small and opposite charges.
The potential difference causes current to flow, creating a threedimensional electric field.
When the top of the meter is placed against one side of a
material with moisture on or slightly below its surface, the
increased capacitance of the material distorts the electric field to
an extent that can be sensed (as a change in flux over the
sensing area) and measured.
The MM9 has been calibrated at the factory for use with drywall,
cement board, softwood and hardwood. The capacitance of
wood and the capacitance of building materials are affected
differently by moisture because they have different densities.
The meter compensates for density by adjusting the gain of its
internal sensing circuitry.
1
The MODE button on the front of the meter provides a
convenient way to switch among the four materials. The name of
he material selected appears on the LCD, which displays the
t
abbreviation REL, shorthand for RELative moisture measurement
mode. Below the LCD is a bank of colored LEDs that roughly
mirrors the digital reading above it in bar graph format, with
green indicating “relatively dry” (with a moisture level below
30%), red indicating “relatively wet”, with a moisture level above
70%, and yellow indicating a level between those two values.
An audible out-of-range alarm (beeper) sounds whenever wood
is tested and found to have a moisture content above 16%,
and when drywall or cement board is found to be more than
70% wet.
Although relative moisture readings have no specific value or
accuracy, they are nonetheless useful for quickly comparing the
moisture levels of materials, or the wetness of different areas of
the same material. For example, you can use the meter to locate
the source of a water leak above a ceiling by comparing
readings at various points on it. If the ceiling is level, the point
that produces the highest reading is below the source of the
leak.
Any relative reading can be held by pressing the HOLD button on
the front of the meter. This button makes it possible to make a
measurement in a dark place and display it after bringing the
meter into a lighted area.
The MM9 can also be operated in pin mode
. In this mode, the
meter bases its measurements on the relationship between the
moisture content of a material and its electrical conductivity. The
wetter a material, the higher its conductivity.
The two replaceable steel pins at the top of the MM9 serve as
the electrodes of a conductance meter optimized for measuring
moisture content. In pin mode, the meter displays
measurements in the unit %WME (Wood Moisture Equivalent).
For hard materials like wood, the meter’s readings largely reflect
surface moisture content because: 1) Moisture close to a surface
has a greater effect on a reading than moisture deep below it;
and 2) The pins of the MM9 are only 0.35 in. (9mm) long and
therefore cannot be driven deep into a hard material. For softer
materials like soil, paper or powders, readings are more likely to
reflect the average moisture level of the material between its
surface and the penetration depth of the pins (normally far less
than 0.35 in.).
In pin measurement mode, the color of illuminated bar graph
LEDs indicates the same relative moisture level as in pinless
mode: below 30% for green LEDs, above 70% for red LEDs,
and an intermediate level for yellow LEDs.
To extend battery life in both operating modes, the MM9
automatically 1) dims the brightness of its backlit LCD by
one-half after 15 seconds and 2) powers itself off after 1 minute
of inactivity.
The instrument is powered by a “9V”battery (included on the
back of the blister card).
PRODUCT OVERVIEW
ig. 1 shows all of the controls, indicators and physical features
F
of the MM9. Fig. 2 shows all possible display indications.
Familiarize yourself with the position and function of all
components before moving on to the Setup Instructions
and Operating Instructions.
Fig. 1. The controls,
indicators and
physical features
of the MM9
D
A. Hinged, spring-loaded protective pin cover and pinless
sensor
B. High-contrast, white-on-black LCD (see Fig. 2)
C. LED bar graph; mirrors reading on LCD.
MODE
D.
button.
four target options: drywall, cement board, softwood and
hardwood.
measurement of wood or building material.
for at least two seconds
operation.
E. button.
and held
HOLD
F.
button. “Freezes” and releases readout. Also used to
silence out-of-range alarms.
G. Pin cover latch. Press to open cover, provide access to
measurement pins, and begin operating in pin mode. Closing
the cover automatically initiates operation in pinless
measurement mode.
H. Measurement pins
I. Pin mode
check button
J. Pinless sensor contacts
K. Pin cover spring-loaded hinge
L. Pinless sensor contacts
M. Pinless sensing area
N. Battery compartment
2
In pinless mode
In pin mode
, brief presses cycle through
, a brief press selects WME% moisture
Pressed and held
, re-calibrates pinless mode
Pressed briefly
, powers the meter on.
Pressed
for at least 2 seconds, powers the meter off.
CAL
(calibration)
A
B
C
F
E
G
H
I
J
K
and “WET”. The meter will also “beep” at either of two speeds to
reflect the moisture level: slow for an intermediate level (with
ne or more yellow LEDs illuminated), and fast for a high level
o
(with one or more red LEDs lit).
MAKING PINLESS (RELATIVE) MEASUREMENTS
To hold a relative reading, briefy press the HOLD button within
one minute of making the measurement. The display will add the
word
HOLD
to the
REL
indication, and the bar graph LEDs will
“freeze” in their current state (illuminated or not).. If the reading
is above the alarm limit for that material, the out-of-limit alarm
will sound. Press and hold the HOLD button to silence it.
Fig 2. All possible display indications
A. Moisture level readout (a 3-digit value in pin mode,
REL in pinless mode)
B. Indicates operation in pin mode with a wood target
C. Indicates operation in pin mode
D. Indicates operation in pin mode with a building material target
E. Low battery charge indication; replace the “9V” battery when
it appears
F. Indicates a held measurement
G. Moisture measurement unit (%WME in pin mode;
not applicable in pinless mode)
H. Indicates operation in pinless mode with a hardwood target
I. Indicates operation in pinless mode with a softwood target
J. Indicates operation in pinless mode with a cement board
target
K. Indicates operation in pinless mode with a drywall target
SETUP INSTRUCTIONS
INSTALL BATTERY
Open the battery compartment at the bottom of the meter
(Fig. 1, Callout N) by placing a fingernail in the slot on the right
side of the housing where it meets the compartment door. Push
the tab on the door gently to the left until it pops open. Slide the
included “9V” battery into the compartment “terminals-first”,
with the anode (+ terminal) on the right. Swing the door back
toward its closed position until it snaps shut.
MAKING PIN (ABSOLUTE) MEASUREMENTS
To measure the absolute moisture measurment of wood or a
building material
latch (Fig. 1, Callout G). The pin cover will swing open to expose
the two test pins, and the LCD will display the word
(Fig. 2, Callout B) and the pin-mode icon (Callout C) at its right.
Remove the black rubber insulating sleeves from the pins.
To measure wood
Its absolute moisture level will be displayed as a percentage,
with the unit %WME (Fig. 2, Callouts A and G). Simultaneously,
the bar graph LEDs will illuminate to mirror the digital reading.
To measure a building material, press the MODE button to
change the indication on the top line of the LCD from
BLDG
(Fig. 2, Callout D). As with wood, carefully press the test
pins into the sample. Its absolute moisture level will be displayed
as a percentage, with the unit %WME. Again, one or more bar
graph LEDs will illuminate to mirror the digital reading.
In wood measurement mode, the available moisture level range
is 5% to 50%. When the level is below 5%, the LCD will show
__ __ __. When it is above 50%, the LCD will show  ̄ ̄ ̄.
In building material measurement mode, the available moisture
level range is 1.5% to 33%. When the level is below 1.5%, the
LCD will show __ __ __. When it is above 33%, the LCD will
show
 ̄ ̄ ̄
To hold a digital reading
one minute of making the measurement. The LCD will add the
HOLD
word
“freeze” in their current state (illuminated or not).
, power on the meter and press the pin cover
WOOD
, carefully press the test pins into the sample.
WOOD
.
, briefly press the HOLD button within
to the digital reading, and the bar graph LEDs will
to
OPERATING INSTRUCTIONS
To power on the meter, press and hold the
for at least three seconds. (To power off the meter,
Callout E)
follow the same instruction.)
MAKING RELATIVE MOISTURE MEASUREMENTS
To measure the relative moisture level of drywall, cement
board, hardwood or softwood,
LATCH
to swing open the top of the meter. Instead, just press the
MODE button until the name of the target material appears on
the LCD. Then scan the material by gently pressing the pinless
sensing area (Fig. 1, Callout M) on the top of the meter against
the material. Make sure no part of your hand or fingers is
touching, or near, the sensing area. LCD will display the
abbreviation
bar graph LEDs below the LCD will illuminate to place the
material’s moisture level within a spectrum bounded by “DRY”
REL
(for RELative measurement), and, one or more
DO NOT PRESS THE PIN COVER
button (Fig. 1,
MEASUREMENT TIPS
For best results in pinless (relative) mode, press the pinless
sensing area against a flat area of a representative sample of
the target material. The sample’s length and width should
be at least as large as the dimensions of the sensing area:
1.5 x 1.5 in. (38 x 38mm).
Ideally, the material should also be at least 3/8 in. thick. That is
the meter’s maximum measurement depth and the thickness
it is calibrated for. If your sample is too thin, the meter will
measure material beneath it as well and produce an inaccurate
reading. Try compensating for thin samples by stacking them.
Measurements of wood are skewed by two variables: ambient
humidity and the density of the wood species. The best way to
compensate for the effect of these variables is to develop your
own moisture level curves, based on your experience working
with different species of wood on a day-to-day basis.
3
CALIBRATING THE METER
Although the MM9 auto-calibrates each time it is powered on,
ou can manually check its calibration in pin-mode operation,
y
as well as re-calibrate its operation in pinless mode. Perform a
re-calibration or calibration check whenever the meter cannot
produce a reading, or if multiple measurements of the same
sample produce very different readings.
To manually check calibration in pin-mode operation:
1. Power the meter on, open the protective pin cover, and hold
the meter in one hand with the top in the air. Make sure your
fingers are not touching or near the sensing area.
CAL
000
button
101
102
,
.
.
2. Using the end of a paper clip as a tool, press the
below the test pins (Fig. 1, Callout I). The LCD should show a
value between 17.3% and 19.3%. If the reading is outside
this range, the MM9 has an accuracy problem in pin mode.
Contact General's Customer Service to arrange for a repair
or replacement.
To manually re-calibrate pinless mode operation:
1. Power the meter on and hold it in one hand with the top in the
air. Make sure your fingers are not touching or near the
sensing area.
MODE
2. Press and hold the
button until the display reads
Then release the button; this will change the reading to
Wait a few seconds. When the reading changes to
re-calibration is complete.
SPECIFICATIONS
Pin Mode 5 to 50% for wood
Measurement Ranges1.5 to 33% for building materials
Pin Mode±2% for wood and building materials
Measurement Accuracy
Pin Mode Calibration 17.3% to 19.3%
Check Range:
Pinless Mode Maximum 3/4 in. (20mm) in wood;
Sensing Depths3/8 in. (9.5mm) in drywall;
1/4 in. (6.5mm) in cement board
Dimensions of Pinless Sensor
Out-of-Range Alarm Levels >16% for wood
LCD Size
Measurement Resolution0.1% in pin mode
Bar Graph Composition3 each green, yellow and red LEDs
LED BandsFor all materials: green = 0 to 30%,
Auto Power Off Trigger1 minute of inactivity
Operating Temperature32° to 104°F (0° to 40°C)
Storage Temperature14° to 122°F (-10° to 50°C)
Dimensions6.7 x 2.8 x 2.9 in. (178 x 70 x 74mm)
Weight5.6 oz. (160g) without battery
Power Source(1) “9V” battery (included)
1.5 x 1.5 in. (38 x 38mm)
>70% for drywall and cement board
2 in. (51mm) diagonal with
three 0.5 in. (13mm) high digits
yellow = 31 to 70%, red = >70%
Replacement Test Pins
Available
The MM9’s stainless steel
pins are replaceable.
General’s Item #PIN3
contains two pairs of
compatible pins,
each 0.3 in. (8mm) long.
WARRANTY INFORMATION
In the U.S, General warrants its instruments and accessories, and
digital tools against defects in material or workmanship for one year
from the date of purchase unless otherwise stated on the packaging,
manual, and/or marketing materials. General also warrants its nondigital tools products against defects in material or workmanship on
a limited lifetime term. The company will replace or repair the
defective unit, at its option, subject to verification of the defect.
This warranty does not apply to defects resulting from abuse, neglect,
accident, unauthorized repair, alteration, or unreasonable use of the
product.
Any implied warranties arising from the sale of a General product,
including but not limited to implied warranties of merchantability and
fitness for a particular purpose, are limited to the above. General shall
not be liable for loss of use of the product or other incidental or
consequential damages, expenses, or economic loss, or for any claim
of such damage, expenses, or economic loss.
State laws vary. The above limitations or exclusions may not apply
to you.
RETURN FOR REPAIR POLICY
Every effort has been made to provide you with a reliable product of
superior quality. However, in the event your instrument requires repair,
please contact our Customer Service to obtain an RGA (Return Goods
Authorization) number before forwarding the unit via prepaid freight
to the attention of our Service Center at this address:
General Tools & Instruments
75 Seaview Drive
Secaucus, NJ 07094
212-431-6100
Remember to include a copy of your proof of purchase, your return
address, and your phone number and/or e-mail address.
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