USER MANUAL 15
Due to temperature sensor localisation, max sample height is 10mm.
When substance ply is too thick, surface layers will be heated too much and internal –
not enough. This may result in burning the sample or surface incrustation, which will make
drying process difficult and measuring result false.
A sample should be placed in uniformed layers 1÷3mm thick, weighing 1÷10g, depending
on a substance.
11.7 Glass fibre filter
When drying liquids, pastes or substances that may melt or loose liquid during drying, it
is advised to use glass fibre filters.
Filters ensure equal liquid distribution or, in case solid materials, avoiding burning a
sample.
11.8 Selection of drying parameters to the sample material
Selection of proper temperature and drying time is essential to achieve precise humidity
measurement. Drying parameters are selected properly if repeatability is on satisfactory
level, usually between 0,11%.
Parameters choice should be made in 3 steps:
Step 1: Drying temperature is related to the physico-chemical properties of the sample.
It is determined by the number of tests carried out in several successive temperatures,
e.g., at intervals of 10 ° C. Proper temperature is the highest value for which the sample
for a few minutes does not change color and smell. Changing the color or odor indicates
the start of the oxidation of the sample, which changes the properties of the sample, which
usually affects the measurement accuracy.
Step 2: Weight of sample used should be large enough to use the entire surface of the
pan, however, the thinner the layer of sample the better the drying process proceeds. The
top and bottom layers of the material should be dried similarly at the same time. If the
material is covered with shell and some moisture is trapped in the material, user should
disintegrate the material or reduce the drying temperature. For liquid materials is
preferable to use filter which accelerates the drying.
Step 3: Select drying time to chosen mass of sample. To do this, set the moisture
analyzer’s drying time as long as possible and observe the drying process. Minimum
drying time is the one at which the sample doesn’t change its weight by more than allowed
by the examiner measurement error. Proper drying time is designated minimum drying
time with reserve. The percentage value of the reserve must exceed the mass of the
sample dispersion - the drying sample time is proportional to the mass of the sample.
After a few measurements with the designated drying parameters and making sure that
the reproducibility of the results is satisfactory user can proceed to optimize the
measurement time by selecting favorable Drying profile and using Short measurement
mode. Of course you should check that the reproducibility of the results was not
seriously affected.
Sample values for the most common materials are given in the Appendix, however, be
regarded only as preliminary data and it is recommended to carry out the procedure for
parameters selection for the test material.
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