MXMF.Users.Handbook.V2.20.doc
LIT:MXUHB April 2003
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Measurement principle of Karl Fischer method is based on the chemical reaction described above. Which
is to say moisture content is deemed by the quantity of KF reagent that selectively responds to water and
produces anhydrate titrated and needed to react to water completely till end point. The quantity of the KF
reagent is electrically detected as the reagent is titrated into the sample in the water. Karl Fischer method
has two means of detection, volume method and coulometry method, the former of which is employed as
an official measurement. This method requires the reagent which is a chemical agent and thus, doesn’t
stop natural chemical reaction and deterioration of the reagent itself, decreasing factor or water equivalent
in the reagent by getting moisture out of air and reacting to it while keeping and/or using it. In which case,
before measurement, the factor needs to be checked for its quantity of reagent that can be bonded to
water, and the reagent must be carefully stored. As just described, Karl Fischer method requires careful
control, check of the reagent and a complex procedure of operation while the heating method doesn’t,
however it is suitable for detecting moisture content in a material such as vapor or that with very little
moisture in ppm.
Moisture analyzers using infrared absorption method work in the benefit of infrared of a specific
wavelength that is absorbed by water. Moisture content is obtained by the energy ratio of reflected light
when a sample is illuminated by the light whose wavelength is absorbed by water and other two wave
length that are not, in order not to have variance because of material surface’s irregularity or location of the
material. It is suitable for stable measuring of powder and grains continuously.
Neutron analyzers detect moisture by the characteristics of hydrogen whose neutron’s speed is reduced
by water and differs from each material. Fast neutral ray becomes thermal neutron as water in sample
reduces neutron’s speed and thus, by the number of thermal neutron moisture content is measured
non-contact, non-destructively and online without pausing. Typical samples are sintered materials.
Moisture analyzers with crystal oscillation method have a structure with a functional thin membrane on its
electrodes, which senses absorbed moisture crystal that changes crystal oscillator’s frequency. The
analyzer measures the frequency to detect moisture content in the sample. This method is suitable to
measure trace quantity of moisture in gas samples.
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Basics
