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Chapter 3
3.3
TEC Module Theory of Operation
Figure 18 shows the functionality of the TEC module. The following sections detail
the theory of operation for each of the blocks in Figure 18.
3.3.1
TEC Interface
The TEC interface provides optically isolated serial communications between the
TEC board and the microprocessor. Control signals are passed to the TEC board to
set the TEC board status, current limit, and temperature set points. Instructions and
data are sent over the serial interface to the optical barrier. Status and data are
serially passed back to the microprocessor.
3.3.2
Limit DAC
The microprocessor loads the digitally stored current limit value into the current limit
12-bit DAC. The Limit DAC converts the digital limit signal from the
microprocessor to a voltage which becomes the limit voltage for the Bipolar Output
To Microprocessor
Optically
Isolated
Serial Bus
Set Point
DAC
A/D
Converter
Sensor
Select and
Figure 18 - TEC Board Module Diagram
Principles of Operation
Limit DAC
Differential
Amp
Set
Actual
Integral Amp
Amps
Sensor Lines
Limit Set Point
Proportional Amp
PI Loop
Heat/Cool Lines
TEC
Current
29
Bipolar
Output
Stage
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