5 TAKING MEASUREMENTS KD2 Pro
Note: It is important to allow about fifteen minutes for equilibration
between readings, even if the sensor is left in the same location.
If multiple measurements of a sample are made too rapidly in suc-
cession, the sample and needle temperature do not have had enough
time to equilibrate from the previous reading, and the resulting mea-
surement is inaccurate. For best results, the sample should be as
close to equilibrium as possible. You can provide a good environ-
ment for equilibration by placing the KD2 Pro sensor and sample in
an isothermal chamber or Styrofoam box.
5.1 General Best Practices
The quality of the measurements you get with the KD2 Pro can be
strongly affected by your measurement practices. The following sug-
gestions can help you to recognize and avoid pitfalls in data collection
so that you obtain the most accurate data possible.
1. Keep the temperature of the sample as constant as possible
during the measurement. The measurement is made by heat-
ing a needle that is placed in the sample and monitoring the
temperature of the needle. In the case of the SH-1 sensor, one
needle heats while the other one monitors. 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.
f Sample temperature changes during the measurement period
degrade the data and make it difficult for the inverse calcula-
tion to find the correct values for the thermal properties. The
algorithms in the KD2 Pro are several orders of magnitude less
sensitive to these errors than the conventional approach (plot-
ting 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) First, always allow about 15 minutes for samples and nee-
dles to equilibrate with the ambient temperature before
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