7Measurement Tutorial
292 Keysight 34420A User’s Guide
To make a more accurate measurement, the copper test leads of the meter should
be extended closer to the measurement and the connections to the thermocouple
be held at the same temperature.
This circuit will give accurate temperature measurements. However, it is not very
convenient to make two thermocouple connections and keep all connections at a
known temperature. The “Law of Intermediate Metals” eliminates the need for the
extra connection. This empirical law states that a third metal (iron (Fe) in the
example) inserted between two dissimilar metals will have no effect upon the
output voltage provided the junctions formed are at the same temperature.
Removing the reference thermocouple makes the connections much easier.
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