TN - TC - How to Identify a Thermocouple by Wire Color (US ANSI)

Summary/Issue Description

Customers often need to configure their temperature controllers, but frequently they are unsure of the type of temperature sensor (thermocouple) they are using. This could result in incorrect input settings, wrong temperature readings, or system malfunctions. 

Root Cause

There are many types of thermocouples available, each with different characteristics and temperature ranges. While the type is usually specified by the sensor manufacturer, this information may be missing or unclear during installation.

However, thermocouples can often be identified by the color of their wire insulation, according to standard wiring codes. In North America (United States and Canada), the ANSI (American National Standards Institute) color code is commonly used. 

According to this standard:

The red wire is always the negative (-) terminal.

The positive (+) wire color varies depending on the thermocouple type.

Solution

To assist with correct setup, refer to the wire color and use the chart below to identify the thermocouple type. Once identified, select the appropriate input type in the temperature controller settings.

Note: This guide focuses on ANSI color coding. If the sensor was made outside the U.S. or Canada, consult the appropriate international standard (e.g., IEC, JIS) for accurate identification.

Date/Revision History

First review 9/15/2025 V1.0

Author: 

Aimee Rivera, Technical Support Engineer

References

ANSI Color Codes for Thermocouples