Isotech TTI-7-R, Operator'S Handbook Manual

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Introduction
1.3.3 Thermocouple reference junction compensation
The electrical connection between the thermocouple element and the
TTI-7-R input connector is often referred to as the internal reference
junction. All standard thermocouple reference functions are defined
relative to
0°C. To eliminate the physical need to reproduce this
temperature inside the TTI-7-R , the actual connection temperature
is accurately measured with an internal PRT. This temperature is
converted to an equivalent EMF and added to the actual
thermocouple voltage measurement, thereby correcting for the
connection temperature.
For high precision thermocouple measurement applications, i.e.
calibration, an external reference junction may be used. Using an
external reference junction eliminates the uncertainties associated
with reference junction compensation.
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