Appendix B
B–22 TA I
NSTRUMENTS
TGA 2950
Selecting a
Hi-Res
TM
Technique
The Hi-Res
TM
TGA option consists of not one,
but several techniques, which all have the
common characteristic of controlling the thermal
experiment based on changes in the sample
weight. Both absolute weight change and the
rate of weight change can be utilized. These
capabilities add a whole new dimension to TGA
experiments.
Some general guidelines have already been
presented in the previous sections on how to set
some of the parameters involved in using Hi-
Res
TM
TGA. In the next section we consider
more closely why one technique may give better
results than another, and present additional
guidelines for selecting techniques and setting
parameters.
Dynamic Rate
Hi-Res
TM
Ramp
In dynamic rate Hi-Res
TM
mode, one or more Hi-
Res
TM
ramp segments are used with positive
resolution settings. In this mode, the furnace
heating rate is varied between a fixed minimum
and the maximum specified in the ramp seg-
ment, but is never reduced to zero (isothermal).
A mathematical function is used to relate the
rate of weight change (%/minute) to the sample
heating rate (
°
C/minute). Dependant variables to
this function are resolution setting, sensitivity
setting and maximum heating rate. Independent
variables are both short and long-term rates of
weight-change (%/minute), time and tempera-
ture. The result is the ability to directly compute
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