General Tools and Instruments MMD950 - Manual (Page 3)

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INTRODUCTION
Thank you for purchasing General Tools & Instruments’ MMD950 Pin/Pinless
Deep Sensing Moisture Meter with Spherical Sensor and Remote Probe. Please
read this user’s manual carefully and thoroughly before using the meter.
The MMD950 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 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
The meter senses the moisture level of a material using either of two
techniques:
1. Inferring the material’s electrical conductivity from the current flow
induced between a pair of steel pins placed on or into the material. The
wetter a material, the higher its conductivity. The MMD950 comes with a
remote probe consisting of a pair of replaceable stainless steel test pins
at the end of a 46 in. long cable.
2. Measuring the change in the material’s capacitance produced by
the slight spreading of an electric field generated by the meter. When
the meter is powered on, the spherical sensor at its top generates a
three-dimensional electromagnetic wave at radio frequency that
extends about 4 in. (100mm) from the meter. When the spherical
sensor is placed against a wet material, the increased capacitance of
the material distorts the wave’s electric field to an extent that can be
measured. This distortion—called the fringing field effect—is
proportional to the material’s moisture level.
WHICH SENSOR SHOULD YOU USE?
It depends on the application. The spherical 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 remote pin-type probe is the only option because the spherical
sensor can only provide relative readings.