TA Instruments TMA 2940, Operator'S Manual

Page: 89 / 176

TA I
NSTRUMENTS
TMA 2940 3–23
If using liquid nitrogen as a coolant, be sure to follow all
of the safety precautions listed in the front of this
manual for handling liquid nitrogen.
3. Start the run.
Adjusting the coolant during the course of the run
may cause nonlinear heating rates, which will be
reflected in noisy or discontinuous curves.
Techniques
for Improved
Subambient
Operation
In order to perform subambient experiments, the
furnace must work against the coolant in the
furnace reservoir. Ideally, you should use the
least amount of coolant necessary to keep the
furnace drawing power over the entire subambi-
ent range.
To improve the accuracy of your cooling
experiments, the following guidelines have been
suggested:
• Pass the purge gas through a dryer and use
impermeable tubing whenever you are
working at subambient temperatures in
order to remove any moisture in the gas
itself.
Between - 20 and +20
o
C, false transitions may
occur if moisture is present in the sample
environment.
t
CAUTION:
NOTE:
Subambient Experiments