TC M Temperature Controller User Manual V1.08
Electron Dynamics Ltd page
6
compound is used to make the thermal connection. A misconception is that more compound will be
better, but this reduces the thermal connection, always dramatically compromising the temperature
stability.
5.4
Peltier Size
This should be calculated from the manufacturers selection.
It is important that the TEC is not driven beyond its maximum, the device will certainly be damaged
if the maximum current is exceeded. Due to the nature of the peltier device as the drive is
increased above between 60 and 80% of maximum it becomes progressively less efficient and in
this situation will tend to just provide more local heating that heat pumping. This can possibly lead
to thermal runaway if the limit is not set . We feel that there is little point in working the devices in
their inefficient region and recommend that device are run at a maximum of 80% of maximum
drive.
5.5
Drive Limit
On the TC M series the TEC drive limits allow maximum cooling and heating rates. Where the
maximum drive is 100%. So to reduce a 12v device to half power, if we are powered at 12v then
the max and mins should be –50% and 50%.
The situation if powered from 9v would be 9/12 * 100 = 75%
5.6
Important stability issues
Some important factors to remember.
Facilitate faster settling time and response
-
by reducing thermal mass of sample
-
reduce distance between TEC and item being cooled
Improve accuracy by locating sensor near to cooled device as possible.
Reduce thermal load by reducing thermal feedback from heatsink to sample by using thermal
insulation.
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Temperature Controlling
6.1
Off mode
This is purely a mode in which under temperature control the output drive is off. This is intended for
diagnostics or to ensure a failsafe condition.
6.2
On/Off control
This mode of temperature control is the most basic, it benefits from being relatively easy to set up.
Simply specify the setpoint, and dead band. However there are some problems with this approach,
due to full on / full off nature of the output, the temperature stability is relatively poor. Though will
be sufficient for some applications. The other problem is that TEC is cycled fully heating and the
fully cooling, this may cause reliability issues with the TEC itself.
