Idiomas disponibles
Idiomas disponibles
4 Measurement Tutorials
Thermocouple Measurements
A thermocouple converts temperature to voltage. When two wires composed of dissimilar metals are joined, a
voltage is generated. The voltage is a function of the junction temperature and the types of metals in the
thermocouple wire. Since the temperature characteristics of many dissimilar metals are well known, a conversion
from the voltage generated to the temperature of the junction can be made. For example, a voltage measurement of
a T-type thermocouple (made of copper and constantan wire) might look like this.
Notice, however, that the connections made between the thermocouple wire and the internal DMM make a second,
unwanted thermocouple where the constantan (C) lead connects to the internal DMM's copper (Cu) input terminal.
The voltage generated by this second thermocouple affects the voltage measurement of the T-type thermocouple.
If the temperature of the thermocouple created at J2 (the LO input terminal) is known, the temperature of the
T-type thermocouple can be calculated. One way to do this is to connect two T-type thermocouples together to
create only copper-to-copper connections at the internal DMM's input terminals, and to hold the second
thermocouple at a known temperature.
An ice bath is used to create a known reference temperature (0 °C). Once the reference temperature and
thermocouple type are known, the temperature of the measurement thermocouple can be calculated.
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Keysight DAQ970A/DAQ973A User's Guide
