Elcometer 7250 Bedienungsanleitung Seite 4

GUIDANCE NOTES - Moisture
meters measure the electrical
resistance of a material and provide
an indication of the moisture content
of materials. A change from low to
high in the display and green to
red on the scale shows that further
tests are appropriate. Problems arise
from the 'structure' of the material
being tested, the presence of other
conductive material that may affect
the reading and also the correct
method of testing. Factors that may
affect readings include:
• Density of the material - this is
important when interpreting the
moisture content that is acceptable
in a particular material.
• Even the same material will be
variable in composition from one
example to another.
• Ability to absorb moisture -
materials will have different
capabilities to hold moisture in a
satisfactory state.
• Conductivity of substance - most
materials have an inherent
conductivity even if this may be
negligible. Conductivity may
be affected by carbonaceous or
ferrous material content.
• Purity of free water - the
conductivity of water varies with
its purity.
• Surface treatment - certain
surface treatments may be
conductive. Residues may contain
carbonaceous material or have a
misleading high moisture content.
Wood treatments of a salts based
liquid will also affect conductivity.
• Temperature - the electrical
resistance at any given moisture
content increases as the
temperature decreases.
• Timber grain - due to the cellular
structure of timber, readings taken in
the end grain will be less accurate.