National Instruments SCB-68 User Manual download pdf (Page 43)

Using Thermocouples

This chapter describes how to take thermocouple measurements using the

SCB-68. A thermocouple is created when two dissimilar metals touch, and

the contact produces a small voltage that changes as a function of

temperature. By measuring the voltage of a thermocouple, you can

determine temperature using a nonlinear equation that is unique to each

thermocouple type. Thermocouple types are designated by capital letters

that indicate their composition according to the American National

Standards Institute (ANSI) conventions. To determine the type of

thermocouple that you are using, refer to Table 4-1. For more information

on the theory of operation of thermocouples, refer to the NI Developer

Zone tutorial, Measuring Temperature with Thermocouples, at

ni.com/zone.

Table 4-1. Thermocouple Coloring

Thermocouple

Type

Positive Color Negative Color

Thermocouple

Cover Color

Extended

Grade Cover

Color

B Gray Red — Gray

C White/Red Trace Red — White/Red Trace

E Purple Red Brown Purple

J White Red Brown Black

K Yellow Red Brown Yellow

N Orange Red Brown Orange

R Black Red — Green

S Black Red — Green

U Black Red — Green

T Blue Red Brown Blue

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National Instruments SCB-68 User Manual Page 43