Series 3700A System Switch/Multimeter Reference Manual
Section 8: Theory of operation
3700AS-901-01 Rev. D/June 2018
8-11
Figure 112: Fast Alternating Scan block diagram
Reference junctions
A reference junction is the cold junction in a thermocouple circuit that is held at a stable, known
temperature. The cold junction is where dissimilar wire connections must be made. As long as the
temperature of the cold junction is known, the Series 3700A can factor in the reference temperature
to calculate the actual temperature reading at the thermocouple.
The standard reference temperature is the ice point (0 °C). The ice point can be precisely controlled,
and the National Institute of Standards and Technology (NIST) uses it as the fundamental reference
for its voltage-to-temperature conversion tables. However, other known temperatures can be used.
There are two ways for the Series 3700A to acquire the cold junction temperature. It can measure the
cold junction using a thermistor or 4-wire RTD, or you can enter a known temperature value.
