Thermocouples are used in a wide variety of industries. They’re used for everything from industrial control to transportation and even to measure the temperature of your home.

They’re also used in laboratories to measure the temperature of various substances and in analytical chemistry to detect various compounds.

In this post, we’ll talk about how thermocouples work and what the thermocouple colour code means.

Understanding How Thermocouples Work

The thermocouple is a temperature sensor made up of two wires wrapped together at the ends.

As the temperature changes, it will change the resistance of the wires. The two wires are different types of metal, which is why they are exposed this way.

When you place them against a surface, you can use something like a voltmeter to measure their resistance. If the object’s surface is hotter than room temperature, it will read as an increased voltage level. If it’s cooler than room temperature, it will read as low voltage.

As your thermocouple gets closer to its target temperature, its resistance reaches equilibrium. That’s why you have to calibrate thermocouples when manufactured to know where their target and equilibrium temperatures are on the scale.

How To Measure Temperature With A Thermocouple

The voltmeter that we use to measure the voltage level of the thermocouple needs to be rated for high temperatures because such high temperatures would damage a regular voltmeter. The voltage in the thermocouple can be so high that you could damage your voltmeter.

With this in mind, you’ll need to know how much voltage can get out of a specific thermocouple. This helps you know where it is applicable.

Thermocouple Voltage Input Specifications

As a general rule, every type of thermocouple has its own unique specifications. One thing that all thermocouples have in common is that they are used with a voltage meter. Voltmeters have different specifications depending on what they are used for.

The Different Color Codes of Thermocouples

The color codes of thermocouples are a way to quickly understand which end of a thermocouple is hot and which is cold. When using your thermocouple, it’s important to know what color represents which end. Here are the different color codes of thermocouples.

Black and Red Thermocouple

This is a type of thermocouple that is used in the measurement of both temperature and voltage. The black wire refers to a constant connection; in this case, it connects to the negative terminal on your voltmeter.

Black also refers to negation while red indicates positive; thus, we call this type of thermocouple black & red. Black indicates the negative end, while red signifies the positive.

Red and Blue Thermocouple

Another type of thermocouple is the red & blue one, which has the same functions as black and red except for its color code (red & blue). The two colors are for temperature and voltage, respectively.

Red and Yellow Thermocouple

This is another type of thermocouple that has its own color code. It’s red & yellow. Red denotes ambient temperature, while yellow is for hot temperature. In other words, red indicates a cold temperature while orange indicates a hot temperature.

Red and Green Thermocouple

A red & green thermocouple is used to measure the flow of gases, which means its thermal conductivity monitor gases. The flow rate can be calculated by measuring hot inlet and cold outlet temperatures at different gas or liquid flow rates that apply to this type of thermocouple at a certain pressure drop between the two points in question. The measurement can then be converted into an internal convective heat transfer coefficient (HTC).

Red and White Thermocouple

The red & white thermocouple is used for measuring liquid levels like in a tank. It’s also used for measuring low-temperature levels, which is about 200 degrees F. It also has a solid-state output that’s easily interfaced with various instruments in the lab or production line.

So, What Is The Color Code of a Thermocouple?

The color codes on thermocouples help you identify the type of thermocouple you’re using and what kind of connection it has to your circuit. Knowing how to read these codes is important because knowing how they work will help you understand your circuit’s functionality and ensure that you don’t have any wiring problems.