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KD2 Pro Operator’s Manual
5. Good Practices
5. Good Practices
The quality of the measurements you get with the KD2 Pro
can be strongly affected by your experimental technique. The
following suggestions will help you to recognize and avoid pit-
falls in data collection so that the data you obtain can be as
accurate as possible.
1.
Keep the temperature of the sample as constant as
possible during the measurement.
The measurement is
made by heating a needle that is placed in the sample and
monitoring either the temperature of that needle or a sec-
ond needle adjacent to the heater. The heat input is made
as small as possible to avoid thermally driven redistribu-
tion of moisture in the sample. The temperature change
from heating may therefore be only a few tenths of a
degree. Sample temperature changes during the measure-
ment period degrade the data and make it difficult for the
inverse calculation to find the correct values for the ther-
mal properties. The algorithms in the KD2 Pro are several
orders of magnitude less sensitive to these errors than the
conventional approach (plotting temperature vs. log time
during heating and looking for a linear portion of the
graph) but there can still be errors if the temperature
changes too rapidly during a measurement. To minimize
these sources of error:
a. In the laboratory, allow samples and sensors to
come to temperature equilibrium before the measure-
ment starts. Fifteen to twenty minutes is a reasonable
rule of thumb.
