TA Instruments TGA 2950 - Constant Reaction Rate Hi-Res TM Ramp

TA I NSTRUMENTS TGA 2950 B–23
Hi-Res
TM
Option
the appropriate heating rate for the current
weight change conditions.
Because the dynamic rate Hi-Res
TM
mode
reduces heating rate smoothly and only when
necessary, it is the fastest and most reliable of
the various techniques. This mode gives good
results with most temperature separable transi-
tions. It is preferred for fast survey scans of
unknown materials over wide temperature
ranges. If no other criteria exists to select a Hi-
Res
TM
technique, then dynamic rate is the
preferred choice.
Constant Reaction
Rate Hi-Res
TM
Ramp
In constant reaction rate Hi-Res
TM
mode, one or
more Hi-Res
TM
ramp segments are used with
negative resolution settings. In this mode the
heater control system varies the temperature of
the furnace as required to maintain a constant
preselected rate of weight change (%/minute).
Whenever the rate of weight change exceeds the
percent/minute threshold, the heating rate of the
furnace is reduced, even to the point of cooling
if necessary. When percent/minute falls below
the threshold the heating rate is increased up to
the maximum specified for the ramp segment.
Transition resolution is improved because
sample heating is reduced or reversed during
transitions allowing them to complete at the
selected reaction rate before moving on to the
next transition. Figure B.10 on page B-49
shows a good example of a material (sodium
bicarbonate) which was analyzed using a
constant reaction rate ramp at 10
°
C/minute with
resolution setting -4.0.