General MMH800 User manual

4-IN-1 PIN/PAD RH
MOISTURE METER
USER’S MANUAL
MMH800
Please read this manual carefully and thoroughly before using this product.
99 Washington Street
Melrose, MA 02176
Phone [phone]
Toll Free 1-800-517-8431
Visit us at www.TestEquipmentDepot.com

TABLE F C NTENTS
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 –4
Key Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
What’s in the Case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Product verview . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 –7
Setup Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Install Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
perating Instructions . . . . . . . . . . . . . . . . . . . . . . 8 – 10
Measuring Moisture Level . . . . . . . . . . . . . . . . . . . . . 8
Accounting For Temperature and Humidity . . . . . . . 9
Checking Calibration . . . . . . . . . . . . . . . . . . . . . . . . 10
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Maintenance Tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Warranty Information . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Return for Repair Policy . . . . . . . . . . . . . . . . . . . . . . . 12
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INTR DUCTI N
Thank you for purchasing General Tools & nstruments’ MMH800 4-in-1 Pin/Pad
RH Moisture Meter. Please read this user’s manual carefully and thoroughly
before using the meter.
The MMH800 is designed for use in woodworking, water damage restoration,
building construction and home renovation. Examples include:
• Checking for moisture on or below the surface of carpets
• Measuring the surface moisture and/or moisture content of wood,
drywall or concrete before painting, wallpapering, sealing or treating
• Locating water leaks in roofs, floors and walls
• Selecting dry lumber
Because it can measure ambient temperature and humidity in addition to
moisture level, the MMH800 is particularly suitable for water damage
restoration projects.
The meter has two LCDs: one displays moisture level and the other—a split-
screen display—monitors temperature and humidity. A dedicated front-panel
button selects the default temperature unit (degrees Fahrenheit or degrees
Celsius).
The 4-in-1 part of the meter’s name refers to its ability to measure:
1) temperature; 2) relative humidity; 3) moisture level using a pin sensor; and
4) moisture level using a pad sensor. The meter has both kinds of sensors, with
a pair of pins on top and a split metal pad on the back. Both sensors base their
measurements on the relationship between the moisture content of a material
and its electrical conductivity. The wetter a material, the higher its conductivity.
n both cases, the sensors serve as the electrodes of a conductivity meter
optimized for measuring moisture content.
Which sensor should you use?
t depends on the application. The pad sensor is the only choice for measuring
surface moisture of materials like finished wood, paint or wallpaper that cannot
be marred by pinholes. f measurement accuracy is important, the pin sensor is
the better option because pins can detect moisture below the surface that the
pad sensor cannot.
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However, for hard materials like wood or concrete, the meter’s readings mostly
represent surface moisture content because: 1) Moisture close to the surface
has a greater effect on a reading than moisture deep below it; and 2) The
factory-installed pins of the MMH800 are only 0.2 in. (5mm) long and 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 (usually far
less than 0.2 in.). To improve the meter’s overall measurement accuracy, the
MMH800 ships with a 4-pack of longer pins: two are 0.4 in. (10mm) long, and
the other two are 0.6 in. (15mm) long.
Moisture level readings are displayed as percentages on the upper LCD of the
MMH800, which is factory-calibrated for use with wood/paper and building
materials (concrete, bricks, wallboard, etc.). Because moisture affects the
conductivity of wood/paper and building materials differently, the meter
measures their moisture content using different scales:
• For wood and paper, the moisture level measurement range is
5 to 50%.
• For building materials, the range is 1.5 to 33%.
A front-panel button allows you to switch between the two materials. Display
icons indicate which material is being tested, as well as whether the current
reading is considered low, medium or high for the material. Any reading can be
held by pushing another front-panel button; this feature makes it possible to
make a measurement in a dark place, hold it, and display it later in a better-
lighted area. The meter is also equipped with a repeating beeper that beeps
faster with rising moisture level, which makes it easy to detect areas of peak
wetness. The beeper can be disabled without affecting measurements.
The meter also has the following three features:
• t automatically powers off after three minutes of inactivity to extend
battery life
• An icon on the upper display indicates when the meter’s 9V battery
is low on charge
• The protective pin cover can be used to check the meter’s
calibration
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KEY FEATURES
• Pin (intrusive measurement of moisture content) and pad
(non-intrusive measurement of surface moisture) sensors
• Separate 3-digit displays of moisture level
and temperature + humidity
• Selectable wood or building materials measurement mode
• °F/°C unit selection
• Wide measurement range and high accuracy
• Audible and visual indications of high, medium and low moisture
levels
• Holds moisture level readings for convenient viewing later
• Pin cover doubles as calibration checker
• Auto power off function
• Low battery indicator
• Powered by single 9V battery
WHAT’S IN THE CASE
The MMH800 comes in a custom hard carrying case along with a 9V battery,
two pairs of extra test pins (10mm and 15mm long), and this user’s manual.
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PR DUCT VERVIEW
The figure below shows all of the controls and indicators on the front of the
MMH800, as well as the locations of the sensor and battery compartment on
its back.
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A
B
C
D
E
F
G
H
I
K
L
M
P
Q
N
J
FRONT BACK

A. Calibration holes
B. Protective cover
C. Replaceable test pins
D. low/medium/highmoisture level icon (high moisture shown)
E. Wood icon
F. Building materials icon
G. Beeper enabled icon
H. Dual function button: Power on/off (press and hold for >3 seconds);
Backlight on/off (press briefly)
I. Temperature and humidity split-screen display
J. Battery compartment cover
K. Dual function button: Beeper on/off (press and hold for >3 seconds);
Moisture reading hold/release (press briefly)
L. button: Selects wood or building materials
M. button: Toggles between temperature units
N. Split metal pad sensor
O. icon: ndicates display is locked or “frozen”
P. icon: ndicates battery is weak
Q. Temperature/humidity sensor vent
SETUP INSTRUCTI NS
INSTALL BATTERY
To open the battery compartment, turn the meter over and use your thumb to
slide the battery compartment cover down and away from the unit. Plug the
included 9V battery into the wired socket inside the compartment. The
terminals of the battery and the socket mate in only one way, with the smaller
male terminal plugging into the larger female terminal. Close the battery
compartment by replacing its cover and snapping it shut.
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PERATING INSTRUCTI NS
To power on the meter, press the button and hold it for at least three
seconds.
(To power off the meter, follow the same instruction.)
MEASURING MOISTURE LEVEL
To measure the moisture level of wood or a building material, first make
sure that its icon appears on the left side of the display. f it does not, press the
button briefly to toggle between wood and building materials. Next,
decide which sensor to use (the meter’s pins or pad) after considering
their pros and cons presented in the introduction. Either 1) Gently press or push
the pins at the top of the meter on or into the material or 2) Press the split pad
sensor on the back against a flat area of the material, making sure that both
sides of the pad touch the surface being measured.
The MMH800 provides three indications of a material’s measured moisture content:
1. A percentage reading on the upper display.
2. One, two or three droplet icons ( ) on the left side of the upper display
to indicate whether the reading is low, medium or high for the material.
The moisture-level range for each category is different for wood/paper
and building materials; see the Specifications section for the exact
percentages.
3. f enabled (the factory default), the meter’s repeating beeper will sound
at one of three rates (slow, medium or fast) corresponding to the
measured moisture level (low, medium or high). The audible changes
make it very easy to pinpoint areas of peak wetness.
To hold a measurement, press the button briefly. This “freezes” the
display and makes the (lock) icon appear at the right of the reading. This
feature makes it possible to make a measurement in a dark place, hold the
reading, and display it later in a better-lighted area. To release the loc , press
the button briefly again. This makes the icon disappear.
The meter’s beeper is enabled by default. To disable the beeper, press the
button and hold it for at least three seconds. This makes the icon
at the lower left of the display disappear. To re-enable the beeper, press and
hold the button again for at least three seconds. Each time the meter is
powered on, the unit reverts to the default state: beeper enabled.
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Some measurement tips:
1. To locate the source of a leak behind wood, plaster, drywall or a
ceiling, make measurements at different locations. The leak is
where the meter displays the highest reading.
2. Never use force to drive the test pins into a hard surface.
3. When measuring the moisture level of soil, surface readings will be
lower than readings with the test pins deep in the soil.
ACCOUNTING FOR TEMPERATURE AND HUMIDITY
Measurements of wood moisture level 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 in your neighborhood.
For example, the humidity level affects the dryness of interior wood considered
“acceptable” for finishing. n the steamy Deep South, where 60% relative
humidity is the norm, fine carpenters have learned how to work with wood with
11% moisture content. But in bone-dry Nevada, Utah, and Arizona, where 30%
humidity is common, the same piece of wood would have to have less than 6%
moisture to be considered ready for finishing.
Moisture levels are just as important to know when joining wood, but for a
different reason. f two work pieces have different moisture levels when they
are joined, when they dry out they will contract by different amounts at
different rates. n the extreme, the result could be a warped board or a
weakened joint.
Temperature also affects moisture levels to the extent that it affects relative
humidity levels. The hotter the air, the more water it can hold. A relative
humidity level of 50% means that the ambient air is holding only half the
moisture is it capable of holding.
The MMH800’s split-screen lower display can help you develop your own
custom moisture level curves by providing real-time temperature and humidity
readings. Both measurements are made and displayed continuously whenever
the meter is powered on.
The meter’s default temperature unit is degrees Celsius (°C). To change the
measurement unit to degrees Fahrenheit (°F), press the button. Each
time the meter is powered on, the unit reverts to the default °C. f you prefer to
work in °F, you must press the button to begin each measurement
session.
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CHECKING CALIBRATION
As mentioned earlier, the meter is factory-calibrated for measuring the
moisture level of wood and building materials on different scales. To chec the
calibrations, remove the protective cap from the top of the meter, taking care
not to stab yourself with the two sharp pins beneath it. Then flip the cap over
and place the two holes in its top over the meter’s two test pins.
The upper display should read 17.5% ±3% with the meter in wood
measurement mode and 16.4% ±3% in building materials measurement mode.
You can toggle the button to check both calibrations without removing the
protective cap.
f either calibration check produces a readout outside the stated range for that
mode, and the meter is still under warranty, call General’s Customer Service
Department at 212-431-6100 to arrange to return the meter for service or
replacement.
SPECIFICATI NS
Moisture Level Measurement ange 5 to 50% for wood/paper; 1.5 to 33% for building
materials
Measurement Accuracy ±3%
Measurement esolution 0.1%
Temperature Measurement ange 32° to 140°F (0° to 60°C)
Temperature Measurement Accuracy ±2°F (±2°C)
Humidity Measurement ange 25 to 95%
Humidity Measurement Accuracy ±5% from 32° to 104°F (0° to 40°C)
Display Type/Size 99.9 count LCD with 0.56 in. (15mm) high digits
Droplet Icon anges Low/Medium/High moisture: >5%/12%/16% for wood
and paper; >1.5%/17%/20% for building material
Auto Power Off After 3 minutes with 0% reading
Low Battery Warning Level <7V
Operating Temperature 32° to 122°F (0° to 50°C) @<80% relative humidity
Dimensions 7.13(L) x 2.17(W) x 1.57(H) in. (181 x 55 x 40mm)
Weight 4.06 oz. (115g) without battery
Current Consumption <20mADC
Power Source 9V battery (included)
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