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INTRODUCTION
Thank you for purchasing General Tools & Instruments’ MMD900 Pin/Pinless
Deep Sensing Moisture Meter with Remote Probe. Please read this user’s
manual carefully and thoroughly before using the meter.
The MMD900 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 and sub-flooring
• Measuring the surface moisture content of wood, drywall or concrete before
painting, wallpapering, sealing or treating
• Locating water leaks above ceilings, below floors or behind walls
• Selecting dry lumber
WHICH SENSOR SHOULD YOU USE?
MMD900 is equipped with a pinless sensor and a pin sensor. The pinless
(capacitive) sensor is the only choice for estimating the surface or internal
moisture level of materials like finished wood, paint or wallpaper that cannot be
marred by pinholes. If accurate readings are important, the pin sensor is the
only option because the pinless sensor can only provide relative readings.
The distinction between absolute and relative readings is important to
understand. The moisture level measurements made by either pair of test
pins—on the instrument or on the remote probe—are displayed in units of
%WME (Wood Moisture Equivalent) simultaneously on a 6.0 to 87.6 count
digital LCD and a 40-LED analog bar graph. Pin measurements are accurate
within 3% of the reading plus 5 digits.
By contrast, readings made by the pinless sensor are simultaneously displayed
with no units on the LCD and on a second scale (called REL) of the bar graph.
Although the pinless readings have no accuracy specification, they are
nonetheless useful for quickly comparing the moisture levels of materials, or
the wetness of different areas of the same material. Two possible uses for the
relative readings are:
1. Determining whether two pieces of wood to be joined have roughly the
same moisture content (which means they will dry out at the same rate
without warping).
2. Locating the source of a water leak above a ceiling, by comparing the
REL readings at various points on it. If the ceiling is level, the point with
the highest REL reading is below the source of the leak.
MMD900 Manual_FINAL_Ra-cond_LANG_080513_awb 8/5/13 4:54 PM Page 3
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