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the top and bottom of the TE module and provide structural integrity as
well as electrical insulation from, and thermal conduction to, the heat sink
and the device being cooled or heated.
Model 300 Series Temperature Controllers are designed to control the rate
and amount of cooling or heating through the use of a feedback loop. The
arrangement of the TE module in the cooling mode is shown in Figure 3.
When a positive DC voltage is applied to the n-type element, electrons pass
from the p-type to the n-type elements and the temperature decreases as
heat is absorbed by the cold side of the TE module. The heat absorbed is
proportional to the amount of current flowing through the TE module and
the number of p-type and n-type elements in the TE module.
+ –
P-TYPE N-TYPE
Heat Dissapated To Heat Sink
Current Flow
Cooling Mode
Th (Hot Side)
Tc (Cold Side)
TE + (Pins 1, 2)
TE – (Pins 3, 4)
Heat Absorbed From Device Being Cooled
+–
Figure 3: TE module configuration
It is necessary to remove the heat from the hot side of the TE module. The
amount of heat to be dissipated is equal to the heat pumped from the cold
side plus the input power to the TE module. Although the amount of
cooling is proportional to the current flowing through the TE module, the
power dissipated by Joule heating (input power heating) in the TE module
is proportional to the square of the current. Half of this heat must be
pumped from the cold side of the TE module. When exceeding a maximum
current value (Imax), which is device dependent, the net cooling of the TE
module decreases because Joule heating is increasing at a greater rate than
Peltier cooling. The manufacturer of the TE module will state the maximum
current for each TE module and this current value should not be exceeded.
The LIMIT SET feature on the Model 300 Series Temperature Controllers
allows you to limit the maximum current flowing through the TE module.
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