General Tools MMD4E Digital Moisture Meter
INTRODUCTION
Thank you for purchasing General Tools & Instruments’ MMD4E Pin-Type LCD Moisture Meter. Please read this user’s manual carefully and thoroughly before using the instrument. The MMD4E is designed for use in woodworking, water damage restoration, building construction, and home renovation. Examples include:
- Checking for moisture on or beneath the surface of carpets, sub-flooring, ceilings, and walls
- Measuring the surface moisture content of wood and building materials before painting, wallpapering, sealing, or treating
- Selecting dry lumber
KEY FEATURES
- Includes separate moisture-resistance curves for wood and building materials
- 9-count green backlit LCD w/0.3 in. high digits
- Low, medium, and high moisture level lights
- Audible high moisture alert
- Reading HOLD button
- Replaceable stainless steel test pins
- Pin cap doubles as calibration checker
- Low battery indication
- 3-minute Auto Power Off
- Powered by “9V” battery (included)
- 1-year limited warranty
WHAT’S IN THE PACKAGE
The MMD4E comes in a blister pack with a factory-installed “9V” battery. Two replacement 9mm (0.35 in.) long test pins— General Part No. PIN3DE—are included.
PRODUCT OVERVIEW
Fig. 1 on the next page shows all of the controls, indicators, and components on the front and top of the MMD4E, as well as the location of the battery compartment on its back.
- Protective pin cap with calibrating resistor inside
- Test pins with black rubber sleeves (sleeves not shown)
- LCD
- Blue LOW moisture level LED
- MODE Toggles between wood and building materials measurement modes
- Green MID moisture level LED
- Red HIGH moisture level LED
- Measurement HOLD button.
- Pressed briefly, “freezes” display readings. Pressed and held, silences beeper until the meter is powered off.
- POWER BUTTON. Press briefly to the power meter on; press and hold for >2 seconds to power the meter off.
- Battery compartment (on back)
OPERATING INSTRUCTIONS
To measure a moisture level
- Remove the pin
- Remove the black rubber protective sleeve from each test
- Press the “POWER” button to power the meter The meter will sound one beep and the LCD will illuminate with a green backlight and the following readout: _BLDG _%
- If you are measuring the moisture coWntOeOnDt of wood, skip ahead to Step 5. To measure the moisture content of a building material, press the MODE This will change the display to the following:
- Carefully press the test pins into the material whose moisture level you wish to measure. The level will be displayed as a percentage. The following tables show the display indications for all possible moisture level readings in Wood and Building Materials Measurement modes.
Wood Measurement Mode Reference Table
| Moisture Level | Display Indication(s) | |
| <5% | _ _ . _% | |
| 5% to 11.9% | XX.X% + blue LOW LED | |
| 12% to 15.9% | XX.X% + green MID LED | |
| 16% to 50% | XX.X% + red HIGH LED + beeper | |
| >50% | _ _ _
. % + red HIGH LED + beeper |
Building Materials Measurement Mode Reference Table
| Moisture Level | Display Indication(s) | |
| <1.5% | _ _ . _% | |
| 1.5% to 16.9% | XX.X% + blue LOW LED | |
| 17% to 19.9% | XX.X% + green MID LED | |
| 20% to 33% | XX.X% + red HIGH LED + beeper | |
| >33% | _ _ _
. % + red HIGH LED + beeper |
To hold any reading (“freeze” the display), briefly press (but do not hold) the HOLD button. To release the hold, briefly press the HOLD button again. This feature allows you to make a measurement in a dark place or around a corner, hold the reading, and display it within 3 minutes later where the lighting is better. Measurements can be held for no more than 3 minutes—the duration of the meter’s Auto Power Off trigger.
To power off the meter, press the “POWER” button and hold it for more than 2 seconds.
To silence the beeper at any time, press and hold the HOLD button for >3 seconds. This will disable the beeper until the meter is powered off. The beeper will automatically be re-enabled when the meter is powered on again.
CHECKING CALIBRATION
You can verify the accuracy of the MMD4E’s readings by manually checking its calibration at any time. To do so:
- Remove the black rubber protective sleeves from the test
- Remove the pin cap and note the small circuit board attached to the inside of its rear The rear wall also has two small holes (left photo below) that provide access to terminals on the circuit board. The circuit board contains a resistor whose fixed value can be used to simulate a precise moisture level and therefore check the calibration of the meter.
- Power on the meter and push the test pins into the calibration holes (right photo below). If the meter is properly calibrated, the displayed reading will be 18.3% ± 1% in Wood Measurement If you do not obtain a reading within this range and your 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.
SPECIFICATIONS
OPERATING, MAINTENANCE & SAFETY TIPS
- Some measurement tips:
- 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 For example, the humidity level affects the dryness of interior wood considered “acceptable” for finishing. In 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.
- To locate the source of a leak behind the wood, plaster, drywall, or ceiling, make measurements at different locations. The leak is where the meter displays the highest
- Never use force to drive the test pins into a hard
- When measuring the moisture level of soil, surface readings will be lower than readings with the test pins deep in the
- When the BATTERY icon appears at the upper left of the LCD, it’s time to replace the “9V” battery that powers the instrument (although measurements will remain valid for several hours after the icon first appears). To replace the battery, turn the meter over and open the battery compartment (Fig. 1, Callout J) by using your thumb to slide the compartment cover down and away from the meter. Plug a fresh “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.
- Do not operate the MMD4E in the presence of flammable or explosive
- Be careful not to stab yourself with the extremely sharp test
- Replace the pin cap and black rubber protection sleeves after making measurements
- for safety reasons and
- to avoid bending or dulling the pins.
- After subjecting the meter to a large change in ambient temperature, wait at least 30 minutes before making measurements to guarantee the accuracy of
- Remove the battery when storing the unit or when you do not expect to use it for an extended period of time (months rather than weeks).
- Do not drop or disassemble the MMD4E or immerse it in Doing so voids the 1-year limited warranty.
WARRANTY INFORMATION
In the U.S., the General warrants its instruments and accessories against defects in material or workmanship for one year from the date of purchase. General 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.
FAQ’s
The wood may have absorbed moisture from the air in your attic. This can cause the wood to appear wet even though it is dry. If you are concerned about the moisture content of your wood, you should use a different method to determine if it is dry enough for use. For example, you could use a moisture meter that measures the moisture content of wood by using a probe that is inserted into the wood (see “Moisture Meters for Wood” on page 2). General Tools & Instruments MMD4E Digital Moisture Meter
I believed the indicated range of error to be unclear. According to the report, it was within 3% of the reading. However, the reading’s measurement units are expressed in %. So I contacted the manufacturer the following, inquiring as to whether a reading of, instance, 10% meant that the error range was between 9.97 and 10.03% or between 7 and 13%.
ABSOLUTELY! It shows you the precise dampness where contacts strike wood, which is exactly what you need. On the face, directly beneath the word GENERAL, there is a tiny button that lets you choose between concrete and wood.
Although I occasionally use mine to check for water penetration on floor joists, I have never used it in a crawl hole in the ground. It worked just fine there.
Thickness has no bearing. It gauges the amount of moisture around the area where the probes make contact. The possible variance throughout is greater for larger pieces of wood. Test several locations if the answer is a question. It works perfectly for split construction lumber or firewood.
This meter is quite accurate. If the moisture is just above or below the surface, I think it would. To assess the material’s resistance, the pins must come into contact with moisture. The resistance decreases with increasing moisture, so the meter will register a higher percentage of moisture. Additionally, General Tools manufactures a painless meter that measures moisture up to 3/4 of an inch below the surface using an RF signal. A broader region can be scanned with ease.
Yes, however, you should ignore the coolers and noises. For usage with a stove or fireplace insert, you desire a moisture level of 15-20%. Lower for outdoor pit or open fireplace.
Worked nicely on the home’s wood floors. I don’t see why it wouldn’t also function on a wood deck. Used it on the wallboard as well.
It will, indeed. Works fairly well.
It requires a 9-volt battery, the same kind we use in our smoke alarms at home.
Given that it is testing surface wetness, the moisture level must be pretty high.
There will be too much moisture in the dough. Over 30%, which is the upper limit.
Yes, moisture will gravitate to the bottom of the carpet and pad if it is there. After inserting the pins, take a reading. The alarm will ring if it is high.
