General Tools and Instruments MMD900 - Manual (Page 9)

To use the remote probe, remove the small rubber yellow plug from the jack
on the right side of the meter (callout P of the figure). Then insert the white plug
at the end of the cable into the jack.
To make a surface moisture level measurement, press the Mode button as
many times as necessary until the text “%WME” appears on the top line of the
LCD. Then press the test pins of the meter or the probe against the target
material. The material’s surface moisture level will be displayed as a
percentage on both the LCD and the LED bar graph.
The bar graph uses LEDs of three different colors (green, yellow and red) to
indicate different moisture level ranges (low, medium and high, respectively).
Readings below 17% are considered low, readings between 17% and 30%
medium, and readings above 30% high. If the beeper is enabled with the
factory-default setting, it will beep faster the higher the moisture level rises
above 17%.
To gauge the internal or surface moisture level of a material, enter REL
mode by pressing the Mode button as many times as necessary until the text
REL appears on the top line of the LCD. To establish a baseline for relative
readings, press the area of the back cover marked “Pinless Sensor” against a
material known to be completely dry. The meter should read “0” on both the
LCD and LED bar graphs. Then press the back of the meter against one or more
points on the target surface and compare the readings.
Some measurement tips:
1. For best results, press the pinless sensor against a flat area of the target
material.
2. When holding the sensor against a material, keep your hand and fingers
as far away from the sensing area as possible.
3. The dimensions of the target surface should be at least as large as those
of the sensing area: 1.6 x 1.6 in. (40 x 40mm).
4. Never use force to drive the test pins into a hard surface.
5. Measurements of wood 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.
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