ETI 7000 Operating Instructions page 2

GUIDANCE NOTES - ETI 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.
Timber adhesive - composite materials
•
such as plywood will give artificially high
readings due to adhesive content.
Homogeneity - different densities in a
•
material, such as knots in wood will
produce erroneous results.
• Electrical contact - it is important to
maintain good contact between the
pins and the measured substance. Hard
surfaces may require 1.2 mm diameter
holes to be drilled.
• Moisture gradient - the moisture content
of a material may vary across it's section
due to various factors.
As a general rule of good practice, results
should be obtained from different areas of
the material. If in any doubt then the (Oven
Dry) test method should be used. A linear
scale is provided for relative measurement,
therefore, facilitating the comparison of
unknown moisture measurements against
known standards obtained by the (Oven Dry)
test method, i.e.:
Wet Weight - Dry Weight x 100 = MC%
Wet Weight
Testing and calibration of ETI moisture meters
is carried out using electrical resistance as the
basis for measurement. Standard resistance
values are verified by empirical testing in
accordance with OIML R 92. moisture
meters - verification methods and equipment:
general provisions, issued by Organisation
Internationale De Métrologie Légale, - 1989.
In conclusion, it must be reiterated that
the meter reading is only a guide as to
the 'dampness' of the material under test.
Knowing the actual moisture content does not
indicate whether that material is 'dry' or 'wet'.
WARNING: Please ensure that there
!
are no electrical cables, water or gas
pipes below the surface of material
being tested.
Wood Reference Table
Wood 1
Afara
Ash; European
Ash; Japanese
Balsa
Banga Wanga
Bosquiea
Boxwood; Maracaibo
Cyprus; E African
Dahoma
Fir; Grand
Gum; American Red
Gum; Spotted
Gurjun
Kapur
Karri
Kuroka
Maple; Pacific
Maple; Rock
Maple; Sugar
Myrtle; Tasmanian
Oak; American Red
Oak; American White
Oak; European
Oak; Japanese
Padang
Panga Panga
Pine; Lodgepole
Pine; Scots
Pine; Yellow
Popular; Black
Pterygota; African
Redwood; Baltic European
Rosewood; Indian
Sterculia; Brown
Tallowwood
Walnut; American
For a more extensive list of timbers and average moisture %age correction, please contact the
ETI Sales Office.
Wood 2
Ayan
Beech; European
Blackbutt
Camphorwood; E European
Cedar; Western Red
Chestnut
Danta
Greenheart
Hemlock; Western
Jarra
Jelutong
Larch; European
Larch; Japanese
Loliondo
Missanda
Niangon
Oak; Tasmanian
Pine; American Long Leaf
Pine; American Pitch
Pine; Caribbean Pitch
Pine; Corsican
Pine; Hoop
Pine; Nicaraguan Pitch
Pine; Ponderosa
Pine; Radiata
Pine; Sugar
Sapele
Seraya; Red
Silky Oak; African
Silky Oak; Australian
Spruce; Norway European
Spruce; Sitka
Stringybark; Messmate
Stringybark; Yellow
Turpentine
Walnut; European
Walnut; Queensland
Whitewood
Yew