General MM7 User Manual

PIN-TYPE LCD MOISTURE METER

WITH TRICOLOR BAR GRAPH

USER’S MANUAL

MM7

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INTRODUCTION

Thank you for purchasing General Tools & Instruments’ MM7
Pin-Type LCD Moisture Meter with Tricolor Bar Graph. Please
read this user’s manual carefully and thoroughly before using
the instrument.

The MM7 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 MM7 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 MM7 serve as
the electrodes of a conductance meter optimized for measuring
moisture content. 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 MM7 are only 0.3 in. (8mm) long and

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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 0.3 in.).

The MODE button on the front panel provides a convenient way
to switch between testing wood and building materials. When
the MM7 is powered on, it automatically enters wood
measurement mode.

Below the LCD is a analog bar graph comprising three banks of
different-colored LEDs. The LEDs light up in sync with changes
in the digital readout.

As the test pins are moved around a sample, or moved among
samples, the color of the right-most “lit” LED (green, orange or
red) may change. Any such change indicates a sizable difference
in the moisture content of different areas of the same sample, or
of different samples of wood or building material.

See the Specifications table on page 3 for the different moisture
ranges of wood and building materials indicated by the three
LED bar graph bands.

To extend battery life in both operating modes, the MM7
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 in the
package).

1

PRODUCT OVERVIEW

ig. 1 shows all of the controls, indicators and physical features

F
of the MM7. 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 MM7

Fig 2. All possible display indications

A. Moisture level readout
B. Indicates operation in wood measurement mode
C. Indicates operation in pin mode
D. Indicates operation in building material measurement mode
E. Low battery charge indication; replace the “9V” battery when

it appears
F. Indicates a held measurement
G. Moisture measurement unit (%WME)

SETUP INSTRUCTIONS

INSTALL BATTERY

Open the battery compartment at the bottom of the meter
(Fig. 1, Callout J) 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. Remove
the “9V” battery from the packaging and slide it into the
compartment “terminals-first”, with the anode (+ terminal) on
the right, as indicated by the markings inside the compartment.
Swing the door back toward its closed position until it snaps
shut.

A. Removable pin cover with fixed calibration-checking resistor

on its underside

B. High-contrast, white-on-black LCD (see Fig. 2)

C. LED bar graph; mirrors reading on LCD

D.

HOLD

button. “Freezes” and releases LCD and LED readouts.

Also used to enable and silence out-of-range alarms.

E. button.

and held

F.

MODE

measurement of wood or building material.

G. Calibration holes sized for the MM7's measurement pins

H. Measurement pin covers

I. Measurement pins

J. Battery compartment

Pressed briefly

for at least 3 seconds, powers the meter off.

button.

Pressed briefly, selects WME% moisture

, powers the meter on.

Pressed

OPERATING INSTRUCTIONS

To power on the meter, press and hold the
Callout E)

follow the same instruction.)
To measure the moisture level of wood or a building material,

power on the meter and remove the pin cover (Fig. 1, Callout A)
by squeezing it gently to pop it off. The LCD will display the word

WOOD

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

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

2

for at least three seconds. (To power off the meter,

(Fig. 2, Callout B) and the pin-mode icon (Callout C) at its

, carefully press the test pins into the sample.

(Fig. 2, Callout D). As with wood, carefully press the test

￣￣￣

.

button (Fig. 1,

WOOD

to