General Tools MM9 Combo Moisture Meter

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 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 three-dimensional 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 can be operated in either of two modes. One is pinless (non-invasive). In this mode, the meter can detect 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.

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.

PRODUCT OVERVIEW

Figure 1 shows all of the controls, indicators, and physical features of the MM9. Figure 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.

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.

D. MODE button. In pinless mode, brief presses cycle through four target options: drywall, cement board, softwood, and hardwood. In pin mode, a brief press selects WME% moisture measurement of wood or building material. Pressed and held for at least two seconds, re-calibrates pinless mode operation.

E. button. Pressed briefly, powers the meter on. Pressed and held for at least 2 seconds, powers the meter off.

F. HOLD 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 CAL (calibration) check button

J. Pinless sensor contacts

K. Pin cover spring-loaded hinge

L. Pinless sensor contacts

M. Pinless sensing area

N. Battery compartment

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.

OPERATING INSTRUCTIONS

To power on the meter, press and hold the button (Fig. 1, Callout E) for at least three seconds. (To power off the meter, follow the same instruction.)

MAKING RELATIVE MOISTURE MEASUREMENTS

To measure the relative moisture level of drywall, cement board, hardwood, or softwood, DO NOT PRESS THE PIN COVER 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. The LCD will display the abbreviation REL (for RELative measurement), and, one or more bar graph LEDs below the LCD will illuminate to place the material's moisture level within a spectrum bounded by “DRY” and “WET”. The meter will also “beep” at either of two speeds to reflect the moisture level: slow for an intermediate level (with one or more yellow LEDs illuminated), and fast for a high level (with one or more red LEDs lit).

MAKING PINLESS (RELATIVE) MEASUREMENTS

To hold a relative reading, briefly 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.

MAKING PIN (ABSOLUTE) MEASUREMENTS

To measure the absolute moisture measurement of wood or a building material, power on the meter and press the pin cover latch (Fig. 1, Callout G). The pin cover will swing open to expose the two test pins, and the LCD will display the word WOOD (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, carefully press the test pins into the sample. 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 WOOD to 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, briefly press the HOLD button within one minute of making the measurement. The LCD will add the word HOLD to the digital reading, and the bar graph LEDs will “freeze” in their current state (illuminated or not).

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.

CALIBRATING THE METER

Although the MM9 auto-calibrates each time it is powered on, you can manually check its calibration in pin-mode operation, 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.
2. Using the end of a paper clip as a tool, press the CAL button 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.
2. Press and hold the MODE button until the display reads 101. Then release the button; this will change the reading to 102. Wait a few seconds. When the reading changes to 000, re-calibration is complete.

SPECIFICATIONS

Replacement Test Pins

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 non-digital 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.