General Tools and Instruments MMH800 - Manual (Page 4)

However, for hard materials like wood or concrete, the meter’s readings mostly
represent surface moisture content because: 1) Moisture close to the surface
has a greater effect on a reading than moisture deep below it; and 2) The
factory-installed pins of the MMH800 are only 0.2 in. (5mm) long and cannot be
driven deep into a hard material. For softer materials like soil, paper or
powders, readings are more likely to reflect the average moisture level of the
material between its surface and the penetration depth of the pins (usually far
less than 0.2 in.). To improve the meter’s overall measurement accuracy, the
MMH800 ships with a 4-pack of pins: two are 0.4 in. (10mm) long, and the
other two are 0.6 in. (15mm) long.
Moisture level readings are displayed as percentages on the upper LCD of the
MMH800, which is factory-calibrated for use with wood/paper and building
materials (concrete, bricks, wallboard, etc.). Because moisture affects the
conductivity of wood/paper and building materials differently, the meter
measures their moisture content using different scales:
• For wood and paper, the moisture level measurement range is
5 to 50%.
• For building materials, the range is 1.5 to 33%.
A front-panel button allows you to switch between the two materials. Display
icons indicate which material is being tested, as well as whether the current
reading is considered low, medium or high for the material. Any reading can be
held by pushing another front-panel button; this feature makes it possible to
make a measurement in a dark place, hold it, and display it later in a better-
lighted area. The meter is also equipped with a repeating beeper that beeps
faster with rising moisture level, which makes it easy to detect areas of peak
wetness. The beeper can be disabled without affecting measurements.
The meter also has the following three features:
• It automatically powers off after three minutes of inactivity to extend
battery life
• An icon on the upper display indicates when the meter’s 9V battery
is low on charge
• The protective pin cover can be used to check the meter’s
calibration
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