■
6 Determining moisture levels
48
6.1.1 Adjusting to the existing measuring process
The moisture analyser is frequently used in place of other drying
techniques (like the drying oven) because it is easier to operate and
offers shorter measuring times. Consequently, the conventional
measuring process has to be adapted to the device so that comparable
results can be achieved.
• Performing a parallel measurement
Lower temperature setting in the moisture analyser than in the
drying oven technique
• The result achieved with the moisture analyser does not match the
reference
– Repeat the measurement with a changed temperature setting
– Vary the switch-off criterion
• Adapting with the calibration curve or factor
6.2
Sample preparation
Prepare one sample at a time for measurement. This prevents the
sample exchanging moisture with the ambient surroundings. If a
number of samples have to be taken simultaneously, they should be
packed in air-tight containers so as to ensure that they do not change
while they are in storage.
Distribute the sample
evenly
and
thinly
on the weighing pan in order
to achieve reproducible results.
If it is applied unevenly, this causes an inhomogeneous distribution of
heat in the sample being dried, resulting in incomplete drying or an
extension to the measuring time. If the sample is piled up, it heats up
with greater intensity in the upper layers, causing combustion or
encrustation to occur. The high layer thickness or possible formation
of a crust prevents the moisture from escaping from the sample. This
residual moisture means that measurement results achieved this way
are not verifiable and reproducible.