Accounting For Temperature And Humidity; Checking Calibration; Specifications - General MMH800 Manuel De L'utilisateur

MMH800 Manual_FINAL_Ra-LANG-cond__073113_Layout 1 8/5/13 5:02 PM Page 6

ACCOUNTING FOR TEMPERATURE AND HUMIDITY

Measurements of wood moisture level are skewed by two variables: ambient humidity
and the density of the wood species.
For example, the humidity level affects the dryness of interior wood considered
"acceptable" for finishing. In the steamy Deep South, where 60% relative humidity is
the norm, fine carpenters have learned how to work with wood with 11% moisture
content. But in bone-dry Nevada, Utah, and Arizona, where 30% humidity is common,
the same piece of wood would have to have less than 6% moisture to be considered
ready for finishing.
Moisture levels are just as important to know when joining wood. If two work pieces
have different moisture levels when they are joined, when they dry out they will
contract by different amounts at different rates. In the extreme, the result could be a
warped board or a weakened joint. Temperature also affects moisture levels to the
extent that it affects relative humidity levels.
The MMH800's split-screen lower display provides real-time temperature and humidity
readings. Both measurements are made and displayed continuously whenever the
meter is powered on.
The meter's default temperature unit is degrees Celsius (°C). To change the
measurement unit to degrees Fahrenheit (°F), press the
meter is powered on, the unit reverts to the default °C.

CHECKING CALIBRATION

The MMH800 is factory-calibrated for measuring the moisture level of wood and
building materials on different scales. To check the calibrations, remove the
protective cap from the top of the meter, taking care not to stab yourself with the two
sharp pins beneath it. Then flip the cap over and place the two holes in its top over the
meter's two test pins.
The upper display should read 17.5% ±3% with the meter in wood measurement mode
and 16.4% ±3% in building materials measurement mode. You can toggle the
button to check both calibrations without removing the protective cap.
If either calibration check produces a readout outside the stated range for that mode,
and the meter is still under warranty, call General's Customer Service Department at
212-431-6100 to arrange to return the meter for service or replacement.

SPECIFICATIONS

Moisture Level Measurement Range 5 to 50% for wood/paper; 1.5 to 33% for building
Measurement Accuracy
Measurement Resolution
Temperature Measurement Range
6
materials
±(3% of reading + 5 digits) in pin measurement mode
0.1%
32° to 140°F (0° to 60°C)
button. Each time the