User`s guide

270
Chapter 7 Tutorial
Measurement Fundamentals
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.
The T-type thermocouple is a unique case since one of the conductors
(copper) is the same metal as the internal DMM’s input terminals. If
another type of thermocouple is used, two additional thermocouples are
created. For example, take a look at the connections with a J-type
thermocouple (iron and constantan):
Two additional thermocouples have been created where the iron (Fe)
lead connects to the internal DMM’s copper (Cu) input terminals. Since
these two junctions will generate opposing voltages, their effect will be to
cancel each other. However, if the input terminals are not at the same
temperature, an error will be created in the measurement.
Internal DMM
Ice Bath
Ice Bath
Internal DMM
34970A Refresh UG.book Page 270 Wednesday, February 17, 2010 12:34 PM