Decagon Devices KD2 Pro Operator's Manual page 47

KD2 Pro
taking measurements.
(b) Allow around 15 minutes between readings for tempera-
tures to equilibrate.
(c) If measurements are made in a temperature chamber or
water bath, make sure the sample temperature stays rela-
tively constant before the measurement starts. Measure-
ments made while a sample taken from an oven and cool-
ing to room temperature can show significant errors if the
cool rate is too fast. Measurements made while the sampe
is undergoing heating or cooling return large errors and
are less accurate than samples with a stable temperature
(d) When measuring thermal properties in the field, allow fif-
teen minutes or so after sensor insertion for temperature
equilibration.
2. Minimize contact resistance. In granular materials, or in solids
where a hole has been drilled to accommodate the sensor, there
is an additional thermal resistance between the heated sensor
and the material into which the sensor is inserted. This ex-
tra resistance is called contact resistance, and it decreases the
thermal conductivity value registered by the sensor. This ef-
fect can be minimized by applying thermal grease to the sensor
prior to inserting it as described in the Decagon Application
Note "Reducing Contact Resistance Errors in KD2 Thermal
Properties Measurements" located in the Support section of
https://www.decagon.com/thermal. When you drill a hole for
the sensor, make sure the sensor fits in the hole is as tight as
possible. Inject thermal grease onto the needle as needed to
improve contact.
Long read times also decrease the effect of contact resistance.
If you are measuring a sample that might give errors from con-
tact resistance, increase the read time from the default to the
maximum (10 minutes) for most accurate results.
Finally, the TR-1 works best for dry granular materials and
powders that have large contact resistance, try to always use
5 TAKING MEASUREMENTS
43