General Tools Moisture Meter MM7 and MM8

General Tools Moisture meter

Track Down Moisture with a General Tools Moisture Meter

Finding the source of moisture that’s causing the mold issue around your house can is sometimes obvious even a casual observer. But when water stains or discoloration aren’t present, it can be a bear. Two new General Tools moisture meter models can direct you to the source of your issues by showing you the exact moisture content of your wood, drywall, or other building materials.

We’re taking a look at two General Tools styles – the MM7 pin-type and MM8 pinless moisture meters.

10-Second Summary

General Tools MM7 Pin-Type Moisture Meter

  • Uses pins to find the moisture content
  • Settings for wood and general building materials
  • Auto-calibrating with calibration check on pin cap
  • Measurement range from 5-50% for wood and 1.5-33% for other building materials
  • $34.97

General Tools MM8 Pinless LCD Moisture Meter

  • Non-invasive capacitive sensing technology
  • Separate settings for drywall, masonry, softwood, and hardwood
  • Auto-calibrating
  • Measurement range from 0-53% moisture in hardwood, 0-35% moisture in softwood, and relative readings for wallboard and masonry
  • $44.97

General Tools Moisture Meter Breakdown

General Tools MM7

The General Tools MM7 moisture meter uses pins to detect the moisture levels in wood, drywall, and other building materials. If this is a new type of tool for you, the operation is pretty simple.

Start by setting the meter to either the “WOOD” or “BLDG”, push the pins up to the material you’re testing. From there, you can move the meter around to see how the moisture content changes. It’s like playing “hot or cold” to trace down the source of the moisture.

One of the features we really like is the white on black reverse contrast LCD screen. It clearly displays which setting you’re on and the numbers are super-easy to read.

It also has a tricolor LED gauge at the bottom of the screen. As you test material, you’ll notice the LEDs light up from green to orange to red. Whenever the moisture meter determines a test sample to be above 16% for wood or 20% for building material, one or more of the red LEDs will light up and the meter will emit an audible alarm. The alarm will continue to sound until you remove the pins or move to a drier area.

The MM7 General Tools moisture meter has a hold function that keeps your reading on the screen. It also auto-calibrates for detecting materials at least 3/8″ thick. You can check the calibration by removing the pin cover and testing the pins in the calibration holes. If the reading falls outside of the acceptable range (17.3% – 19.3%), it’s no longer reading properly.


General Tools MM7 Specs

  • Range: 5 to 50% for wood, 1.5 to 33% for building materials
  • Accuracy: ±2% for wood and building materials
  • Resolution: ±2% for wood and building material
  • Calibration Check Range: 17.3% to 19.3%
  • Out-of-Range Alarm Levels: >16% for wood, >20% for building materials
  • LCD Size: 2″ diagonal, with three 0.5″ high digits
  • Bar Graph Composition: 3 each green, orange, and red LEDs
  • Dimensions: 6.9″ x 2.8″ x 2.9″
  • Warranty: 1-Year Limited
  • Price: $34.97

General Tool MM8

The General Tools MM8 moisture meter functions almost exactly like the MM7, but with one fundamental difference. Rather than using pins to test moisture, it uses a capacitor plate. This means that you won’t have to physically press pins into your material and leave pinholes behind.

Most of the features are the same. The screen, LED, auto-calibration, and hold features are all here. With the need for a physical connection from pins, the sensor can read up to 3/4″ deep in wood.

There are a few minor differences worth noting as well. For starters, the MM8 has more specific modes to work with.

  • Wall
  • Masonry
  • Softwood
  • Hardwood

The range is also a bit wider for softwoods while the accuracy drops from 2% to 4%. Finally, the moisture alert is slightly higher (17%) for the MM8 and it trips at 70% for drywall and masonry.

General Tools MM8 Specs

    • Range: 0-53% for softwood, 0-35% for hardwood, relative readings for wallboard and masonry
    • Accuracy: ±4% for hardwood and softwood
    • Resolution: ±1%
    • Max Sensing Depth in Wood: 3/4″
    • Out-of-Range Alarm Levels: >17% for wood, >70% for drywall and masonry
    • LCD Size: 2″ diagonal, with three 0.5″ high digits
    • Bar Graph Composition: 3 each green, yellow, and red LEDs
    • Auto Power Off: After 2 minutes of inactivity
    • Operating Temperature:32° to 104°F @5 to 95% RH
    • Weight (without battery): 5.4 oz
    • Power Source: 9V battery
    • Dimensions: 6.9″ x 2.9″ x 1.2″
    • Warranty: 1-Year Limited
    • Price: $44.97

Pricing and Availability

While you can find General Tools products at just about anywhere tools are sold, these particular General Tools moisture meter models are available exclusively from Home Depot. The MM7 retails for $34.97, while the MM8 will cost you $10 more for its pinless design and additional features. Both come with a 1-year limited warranty.

For more information about the General Tools moisture meter options, click here.

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