32 Chapter 3 Principles of Operation
When an LM335 sensor is used, a two-point conversion equation is used to determine
the temperature. Its voltage is measured as well as the I
TE
current.
When an AD590 sensor is used, another two-point conversion equation is used to
determine the temperature. Its reference current is sensed across a resister, and this
voltage is measured. The I
TE
current is also measured.
3.3.9.2 R Mode
In constant R mode, the TEC is driven to the set point resistance, voltage, or current.
This resistance, voltage, or current is measured and converted to a temperature. The
I
TE
current is also measured.
3.3.9.3 I
TE
Mode
In constant I
TE
mode, the TEC is driven with a constant current, at the I
TE
set point
value. The I
TE
current is sensed across a resistor and the voltage is converted to I
TE
current.
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