Tutorial 7
Keysight 34970A/34972A User’s Guide 283
In some measurement situations, however, it would be nice to remove the need
for an ice bath (or any other fixed external reference). To do this, an isothermal
block is used to make the connections. An isothermal block is an electrical
insulator, but a good heat conductor. The additional thermocouples created at J1
and J2 are now held at the same temperature by the isothermal block.
Once the temperature of the isothermal block is known, accurate temperature
measurements can be made. A temperature sensor is mounted to the isothermal
block to measure its temperature.
Thermocouples are available in a variety of types. The type is specified by a single
letter. The table on the following page shows the most commonly used
thermocouple types and some key characteristics of each.
Measurement
Thermocouple
Internal DMM
Reference
Temperature
Reference
Sensor
Isothermal Block
(Internal or External Reference)
The thermocouple conversion routines used by the 34970A/34972A are
compatible with the International Temperature Scale of 1990 (ITS-90).
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