Kett HI-520, Operating Manual

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3. Measurement Principles
The HI-520 is a high frequency capacitance moisture tester which
detects changes in electrical conductivity (high frequency
capacitance) due to moisture content in concrete and mortar to
determine the moisture content.
Taking 1 as the reference conductivity of air, the conductivity of
each type of material is 10 or less. The conductivity of water is
80, a much larger value than concrete or mortar. Therefore when
the concrete or mortar contains water, the conductivity is found
to be higher than with the dry material. This makes it possible to
determine the moisture content by determining the relationship
between moisture content and conductivity beforehand. In
actuality, the HI-520 measures changes high-frequency
capacitance rather than conductivity to determine moisture
content. The values obtained in this way are displayed as the
measured moisture content.
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