How to Check Thermocouple with Multimeter? Updated Correct Guide 2024

It’s important to know How to Check Thermocouple with Multimeter. Because if you’re an industrial electrician then testing a thermocouple or RTD is a must. So, Let’s jump on a step by step guide. Wait on but do you know what a thermocouple is? If No then understand it first.

What is a thermocouple?

A thermocouple is a device that measures temperature changes. It is usually used in industrial applications such as refrigeration and air conditioning systems, or in laboratory applications such as calorimetry.

In addition to that, Thermocouples are also known as resistive temperature detectors or RTDs. If you’re looking for a quality clamp multimeter for these testing then click here!

How to Check Thermocouple with Multimeter

Types of Thermocouple:

Thermocouples are used to measure temperature and are often found in scientific experiments. There are three types of thermocouples:

The three types of thermocouples are the two-wire type, the four-wire type, and the five-wire type. Learn about KAIWEETS KM100 Digital Multimeter.

  • The two-wire type is the most common and has a resistance of 100 ohms.
  • The four-wire type has a resistance of 200 ohms.
  • While the five-wire type has a resistance of 300 ohms.

Applications of the thermocouple

Thermocouples are used in a wide variety of applications and have diverse uses. Some of the most common uses include temperature measurement, power generation and conversion, and thermometry.

Industrial machinery, including pumps, compressors, boilers and turbines, utilize thermocouples as well. Laboratory experiments can also measure the coefficient of heat transfer using thermocouples.

Thermocouples are composed of two wires that are joined at one end by a junction that is attached to an insulated metal block called the “thermocouple junction.” The junction is connected to an electrical circuit that allows current to pass from one wire to the other wire when they are brought into contact with each other. So, its important to know how to check multimeter with thermocouple.

How to Read the Voltage on a Thermocouple with a Digital Multimeter?

How to Check Thermocouple with Multimeter? This article explains how to read the voltage on a thermocouple with a digital multimeter.

This is a question that many people ask when they first start using a digital multimeter, but it is not easy to find an answer. The article provides tips and tricks for reading the voltage on thermocouples with a digital multimeter.

However, when you’re measuring voltage, it is important that you are aware of what type of thermocouple you are using. When using a thermocouple, the direction the red wire is facing should be the positive terminal and the black wire should be negative.

Common Causes of Thermocouples Malfunctioning

Thermocouples are used to measure the temperature of a liquid. There are many problems that can cause thermocouples to break.

Moreover, thermocouples can break due to high or low temperatures, exposure to chemicals, and mechanical damage. Thermocouple breaks can also be caused by the following:

  • Electrolysis
  • Corrosion
  • Long term stress
  • Short circuit in wiring

How to Check Thermocouple with Multimeter

How to Fix a Broken or Out-of-Range Thermometer Using a Multimeter

When troubleshooting, it is important to know the correct settings for the thermometer.

There are two ways to fix a broken or out-of-range thermometer:

1) By setting it to Fahrenheit and calibrating it

2) By replacing the broken or out-of-range part with a new one.

How to Check Thermocouple with Multimeter?

The thermocouple is a device that measures temperature. To do this, it contains two wires with different metals. One wire is heated and the other is cooled. The thermocouple then produces an electric current when the two wires are in contact with each other.

Therefore, to check a thermocouple with a multimeter, you will need to find the resistance of the thermocouple in ohms and then multiply it by 10 to find out its voltage. You will also need to know what type of multimeter you’re using and if your meter has a built-in function for checking thermocouples or not.

There are many digital multimeters available in the market with K-type thermocouples for temperature measurements. You can use them also for thermocouple testing.

Which Digital Multimeters Work Best With Thermocouples?

Digital multimeters are a popular tool among electronics technicians. They are used to test the voltage, current, resistance, and power of electrical circuits. Thermocouples are used in electronics to measure temperature.

Digital multimeters work best with thermocouples when they have a higher voltage range than the thermocouple they are measuring. Therefore, I have dig down three best digital multimeters for thermocouple testing.

Reasons to Check Thermocouple with Multimeter

A thermocouple is a crucial component in many gas appliances, responsible for sensing temperature and sending a signal to regulate the gas flow. When a thermocouple malfunctions, it can lead to a variety of problems, including:

How to Check Thermocouple with Multimeter

  • Pilot Light Issues: A failing thermocouple may not generate enough voltage to keep the pilot light lit. This can cause the appliance to shut off unexpectedly or fail to ignite altogether.

  • Inefficient Operation: In some cases, a damaged thermocouple might still allow the pilot light to function, but it might send inaccurate temperature readings to the control unit. This can lead to inefficient operation and higher gas bills.

  • Safety Concerns: A malfunctioning thermocouple can potentially lead to a gas leak if the gas valve doesn’t receive the proper signal to shut off.

A multimeter is a versatile tool that allows you to test the functionality of a thermocouple quickly and easily. Here are some key reasons why you should consider checking your thermocouple with a multimeter:

1. Troubleshooting Appliance Issues:

If you’re experiencing problems with your gas appliance, such as difficulty igniting, frequent pilot light outages, or inconsistent heating, a malfunctioning thermocouple could be the culprit. Using a multimeter to test the thermocouple can help you pinpoint the source of the issue and determine if a replacement is necessary.

2. Preventative Maintenance:

Regularly checking your thermocouple with a multimeter, especially for older appliances, can be a proactive approach to maintenance. Early detection of a failing thermocouple allows you to address the problem before it leads to a complete appliance breakdown or potential safety hazards.

3. Cost-Effective Diagnosis:

A multimeter is a relatively inexpensive tool compared to calling a technician for appliance diagnosis. By checking the thermocouple yourself, you can save money on service fees, especially if the issue is a simple fix like replacing the thermocouple.

4. Simple and Quick Testing Procedure:

Testing a thermocouple with a multimeter is a straightforward process that doesn’t require extensive technical knowledge. With some basic instructions and safety precautions, you can conduct the test yourself in a matter of minutes.

5. Peace of Mind:

Knowing that your thermocouple is functioning properly can provide peace of mind regarding the safety and efficiency of your gas appliance. A quick test with a multimeter can help ensure your appliance is operating as intended.

Things to Consider Before Testing:

While using a multimeter for thermocouple testing offers several advantages, it’s important to prioritize safety and ensure you have the necessary knowledge before proceeding. Here’s a breakdown of key considerations:

Safety Precautions:

  • Turn Off and Cool the Appliance: This is paramount. Always ensure the gas appliance is completely turned off at the main gas valve and has had sufficient time to cool down before attempting any testing procedures. Residual heat can be deceiving, so allow ample time for the appliance to reach room temperature.

  • Gas Leak Awareness: Be aware of the potential for gas leaks. A faulty thermocouple could be a symptom of a larger issue within the gas system. If you suspect a gas leak, characterized by a strong gas odor, hissing sounds, or discolored flames, evacuate the area immediately and call your gas company or a qualified technician. Do not attempt to troubleshoot or use electrical equipment in the vicinity of a suspected leak.

  • Working Alone: If you’re uncomfortable working with gas appliances, it’s best to seek help from a qualified technician.

Multimeter Knowledge:

  • Understanding Multimeter Functions: Familiarize yourself with the basic functions of your multimeter, particularly the millivolt (mV) setting. Most multimeters have a rotary switch with various settings for measuring voltage (AC and DC), resistance (ohms), current (amps), and continuity. For thermocouple testing, you’ll be using the millivolt (mV) setting.

  • Setting the Multimeter: Consult your multimeter’s user manual for specific instructions on setting it to the millivolt (mV) range. Some multimeters might have multiple millivolt ranges, so it’s crucial to select the appropriate range that can accommodate the expected voltage output of your thermocouple (usually between 0 mV and 100 mV). Setting the incorrect range might result in inaccurate readings.

  • Lead Connections: Identify the red and black test leads of your multimeter. The red lead typically corresponds to the positive terminal, while the black lead is negative. These leads will be used to connect the multimeter to the thermocouple for testing.

Thermocouple Information:

  • Thermocouple Type: Different thermocouple types are designed for specific temperature ranges and generate varying voltage outputs. Knowing the type of thermocouple in your appliance is crucial for interpreting the test results. This information can often be found in the appliance manual or on a label affixed to the thermocouple itself. Common thermocouple types for household gas appliances include K-type and J-type.

  • Expected Millivolt Range: Research the expected millivolt (mV) output of your specific thermocouple type at different temperatures. Thermocouple manufacturers provide reference charts or tables that illustrate this relationship. Having this information allows you to compare your multimeter reading during testing to the expected voltage output for a properly functioning thermocouple under the applied heat. For example, a K-type thermocouple heated to a moderate temperature (around 400°C or 750°F) might generate a voltage output between 20 mV and 30 mV.

  • Thermocouple Condition: Visually inspect the thermocouple for any signs of physical damage, such as corrosion, cracks, or loose connections. These issues can significantly impact the thermocouple’s ability to function properly.


By following these safety precautions, familiarizing yourself with your multimeter’s functions, and gathering information about your specific thermocouple, you can approach the testing process with confidence and ensure accurate results. If you’re unsure about any of these steps or feel uncomfortable proceeding, consulting a qualified appliance technician is always the safest option.

Engr. Amna has been working with on multimeterworld from 2019 and have worked on multiple projects as team leader. He is currently working in JDW Sugar mills and love to write electrical testing guides. His aim is to help 1 million people each year.