PCE Health and Fitness FME User manual

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Manual
Humidity detector for building materials

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1. Characteristics............................................................................................................................................. 3
1.1 Unit density................................................................................................................................................. 3
1.2 Moisture content ........................................................................................................................................ 3
1.3 CEN (European Committee for Standardization).................................................................................... 3
1.4 In Practice ................................................................................................................................................... 4
2. Electric moisture measurement ................................................................................................................. 4
2.1 Outline......................................................................................................................................................... 4
2.1.1 Wood species, building materials and paper................................................................................... 4
2.1.2 Temperature ........................................................................................................................................ 4
2.1.3 Accuracy.............................................................................................................................................. 5
2.1.4 Measuring depth................................................................................................................................. 5
2.1.5 Measuring methods............................................................................................................................ 5
2.1.6 Measuring direction............................................................................................................................ 5
2.1.7 Measuring surface.............................................................................................................................. 5
2.1.8 Measuring range................................................................................................................................. 6
2.1.9 Preservatives....................................................................................................................................... 6
3. Wood species............................................................................................................................................... 6
4. Building materials...................................................................................................................................... 17
5. Paper........................................................................................................................................................... 18

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1. Characteristics
In this chapter the unit density, the oven-dry method and the moisture measurement with the Micro-Electronics
moisture meters are described.
1.1 Unit density
The formula for the unit density is:
(1) Unit density
The unit density is used for moisture measurements with the FMW-B / FMW-T moisture meters.
•For wood, the FMW-B / FMW-T are set at the average unit density applicable for a moisture
content of 0%.
•For building materials and paper, the FMW-B / FMW-T is set at the reference line.
1.2 Moisture content
The average moisture content of a sample is determined using the oven-dry method.
•For wood, a sample of approx. 100-200 gram is weighed and then dried at 102-105 °C, until
the mass of the sample is constant.
•For building materials and paper, we refer to the manual for the relevant measuring
equipment.
The formula for determining the moisture content according to the oven-dry method is:
The Micro-Electronics moisture meters calculate the actual moisture content, as determined by the
oven-dry method.
1.3 CEN (European Committee for Standardization)
EN 13183-1 Round and sawn timber Method of measuring moisture content Part 1: Method for

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determining moisture content of a piece of sawn timber (Oven-dry method)
EN 13183-2 Round and sawn timber Method of measuring moisture content Part 2: Method for
estimating moisture content of a piece of sawn timber (Electrical resistance method)
EN 13556 Round and sawn timber Nomenclature of timbers used in Europa
1.4 In Practice
Wood building materials and paper have an inhomogeneous composition.
•Wood is constructed from various layers and often contains resin ducts, cavities, knots etc.
•Building materials and paper are different in composition and element size.
As a result, variations can occur in the electric characteristics and unit density of samples of the same
type with similar moisture contents and temperature. The smaller these variations are, the greater the
accuracy of the moisture measurement.
2. Electric moisture measurement
Micro-Electronics distinguishes the following two electrical measurement methods for determining the
moisture content:
•Moisture measurement by measuring the electric conduction (FMC, FMD, FME).
•Moisture measurement by measuring the dielectric constant (FMW-B / FMW-T).
2.1 Outline
The following points are important for accurate moisture measurements with the Micro-Electronics
moisture meters.
2.1.1 Wood species, building materials and paper
FMC, FMD, FME FMW-B / FMW-T
Every material has its own
specific electric conduction. Every material has its own specific unit density.
The correct reference values must therefore be set. In chapters “Wood species” and
“Building materials” and “Paper”, the reference values are indicated.
2.1.2 Temperature
FMC, FMD, FME FMW-B / FMW-T

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Wood: As the wood temperature influences
conduction, the correct wood temperature
must be set. There is a choice of two
temperature corrections.
The temperature has virtually no influence
on a correct moisture measurement
2.1.3 Accuracy
FMC, FMD, FME, FMW-B / FMW-T
The material to be measured and the number of measurements determine the final
accuracy of the moisture measurement. The reasons for this include the inhomogeneous
composition and the moisture distribution.
As a rule, the greatest accuracy is obtained when a number of measurements are taken.
2.1.4 Measuring depth
FMC, FMD, FME, FMW-B / FMW-T
Material that has been artificially dried, will have a higher moisture content at the core than
at the edge.
Wood: The moisture content of a piece of wood is determined at about 1/3 of the thickness
of the wood. The reference values are also based on this. If the moisture content of the
core of a thick piece of wood must be determined, the wood can be sawn in two in order to
measure the core more easily.
2.1.5 Measuring methods
FMC, FMD, FME FMW-B / FMW-T
Using insulated measuring pins, the
moisture content is measured between the
non insulated points of the measuring pins.
The moisture content along the whole
length of the measuring pin is measured
using the non insulated measuring pins. It is
typical that the highest moisture content is
always measured between the non
insulated parts of the measuring pins.
The sensor measures the average moisture
content to a depth of 25 mm. Wood: For
wood with a thickness of less than 10 mm,
several sections can be laid on top of one
another. As it is possible to measure
through the material, notice should be taken
of what is behind the wood.
2.1.6 Measuring direction
FMC, FMD, FME FMW-B / FMW-T
In general, it is of no consequence whether
the measuring pins are placed lengthwise or
crosswise. Wood: Preferably crosswise to
the grain.
In general, it is of no consequence whether
the sensor is placed lengthwise or
crosswise. Wood: Preferably crosswise to
the grain.
2.1.7 Measuring surface
FMC, FMD, FME FMW-B / FMW-T