5134_Thermocouple_secret.pdf | | The Secret to Thermocouples - Mind the Metallurgy, and All Else Will Follow
by Mike Bayda, Keithley Instruments, Inc.
Imagine an electronic sensor technology that's simple, cheap, reliable, and 200
years old. Look no farther than the popular thermocouple. In the early 1800s,
Thomas Seebeck discovered that the junction of two metals generates a voltage
that depends on temperature. Many lab students have begun their association
with thermocouples by exploring this relationship with a set-up similar to that
shown in Figure 1. They measure an unknown temperature using a pair of
thermocouple junctions, one of which is immersed in an ice water bath. After
making voltage measurements, they determine the unknown temperature using a
thermocouple look-up table. Today, engineers and scientists use electronic
instrumentation that can accept dozens of thermocouple inputs, without requiring
an ice bath reference or individual reference junctions. How this has been
accomplish |