C-THERM TCi, Operator'S Manual, Page: 8 / 138

TCi Operator Manual
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1.1 A note on instrument limitations
It should be noted that in applying an instrument such as the C-Therm TCi in testing a wide
variety of materials, material types and temperature ranges, careful consideration should be given
to the limitations in performance and/or use of this system under certain conditions. In many
cases, the C-Therm TCi can replace as many as four (4) traditional thermal conductivity
instruments that covered the same claimed range of testing. However, in simplifying thermal
conductivity testing and providing an instrument to test such a wide material range, there are
some limitations that can be encountered in specific circumstances where a general research tool
like the C-Therm TCi will not be appropriate (the proverbial square bolt in a round hole).
As such, every attempt is made to provide up-front information on any known limitations of the
system and to provide general recommendations that help to ensure the optimal use of the
instrument.
Examples of performance constraints that may be encountered and some recommended best
practices include:
 Contact with some materials is poor due to the material morphology or a process
condition and the fact that the sensor chip surface is not flexible or conforming. C-Therm
has provided contact agents for non-porous solid materials testing and can establish
special calibrations for certain materials that are not compatible with liquid contact
agents.
 Like all lab instruments, the C-Therm TCi should be used in a consistent manner to
ensure consistent results. The user’s test methodology is extremely important and it is
recommended users review any new application of the instrument with a C-Therm
technical support person.
 The C-Therm TCi is designed to withstand the full temperature ranges specified, but has
not been calibrated for the entire range given the constraints of available calibration
materials and typical requirements for specific Material Groups. Customized calibration of
the instrument is possible, either by a C-Therm representative or by a user certified for
advanced operation of the instrument.
 The C-Therm TCi is a very sensitive analytical instrument. It is the user’s responsibility to
provide stable environmental conditions in optimizing the performance of the instrument.
As such, the users’ test methodology is important to guarantee accurate and consistent
results (e.g. thermal chambers used in sub-zero temperatures may generate frost
between the sample and sensor, affecting the results. The user needs to compensate
accordingly for these conditions).
 The sensor construction was chosen to meet the optimal combination of test temperature
requirements as well as respecting internal design constraints. Some materials of
construction may be aggressively affected by contact with certain chemicals – it is
necessary to be aware of those chemicals that are known to impact the integrity of the
sensor as well as those that have not been tested or determined through literature
searches to be safe. Appendix C provides a listing to inform users of these issues and
has provided means to test the least resistant component, the RTV sealant. Test tabs
can be purchased from C-Therm for chemical aggression testing, avoiding undue
damage to the sensor. C-Therm will not take responsibility for sensors damaged due to
exposure to untested or known to be damaging chemicals.
 Testing under compression greater than 90 psig can result in a damaged sensor. Special
testing conditions requiring higher-pressure ratings can be investigated on an individual
basis in contacting a C-Therm representative.
The thermal conductivity of the sample material is primarily determined by the direct
measurement of the thermal effusivity (thermal inertia) of the material. In rare circumstances, an
unacceptable error is evident in testing materials which have a density or heat capacity which are
substantially different than the materials applied in the calibration of the system. The Error