Thermocouple vs. IR Pyrometer



Boiler maintenance is a critical measure in power plants. To keep fuel and energy costs low while maximizing output it is essential that the boiler be operating as efficiently as possible. For ideal boiler performance, monitoring the internal atmosphere is crucial. There are two instruments commonly used for reading boiler temperatures, thermocouples and pyrometers. Each type of sensor varies in their capabilities but pyrometers typically don’t face the same constraints as thermocouples. When it comes to temperature measurement, Infra-View® pyrometers provide users with durability, dependability, and versatility.

Principles of Infrared Pyrometers

Infrared pyrometers are sensors that consist of a lens to focus the infrared energy on to a detector. The detector then converts the infrared energy to an electrical signal that can be displayed in units of temperature after compensation for ambient temperature variation.

When a direct contact measurement is not possible, infrared pyrometers are an optimal solution. Pyrometers achieve a non-contact reading by measuring the thermal radiation being emitted by the source. Infrared pyrometers are known as non-contact temperature sensors and known for their ability to monitor temperature and dictate process control in a range of manufacturing processes. Many industrial processes present safety concerns and involve temperatures that are too intense for contact devices like thermocouples.

Advantages of Pyrometers

Infrared pyrometers present a variety of advantages. The configuration of our Infra-View® infrared pyrometer allows it to provide a temperature measurement from a distance without contact. A pyrometer’s continuous measurement leads to advances in process efficiency, product quality, and safety. Both of our sensors have a 30:1 field of view indicating that 30ft from the sight tube there is a 1ft diameter field. Our Infra-View® Pyrometer excels in harsh environments and maintains an accuracy of +-1% of the reading up to 4,500°F.

Principles of Thermocouples

A thermocouple is comprised of two dissimilar metal wires that form a junction. When the junction is heated or cooled, a small voltage is generated in the electrical circuit of the thermocouple. The voltage generated can then be measured and translated into a temperature reading.

The most common thermocouples are Types J, K, T, E, and N, depending on their metallic composition. Types R, S, and B, known as “noble metal” thermocouples, are typically used for higher temperatures. The more common types can read a maximum temperature of up to 2300°F, while the noble metal thermocouples can read temperatures up to 3100°F.

Limitations of Thermocouples

Thermocouples can be used to effectively obtain general surface measurements. Despite their reliability for surface measurements, factors like surface oxidation, ambient temperature of the air, loss of heat through conduction, and the applied pressure of the thermocouple on the surface can influence a thermocouple reading. To obtain an accurate reading, the thermocouple must be in contact with the surface it is measuring. Thermocouples typical field of view ratios can vary from 1:1, 2:1, 10:1, 5:1, 20:1 or 1:2. In severe conditions, the application will destroy a contact type sensor such as a thermocouple.


Infra-View® offers a variety of infrared pyrometers meant for boiler/furnace evaluation and optimization. Our Infra-View® Pyrometer is a remote-sensing infrared detector that is permanently flange-mounted on any port, door, or penetration into a boiler or furnace. Our Infra-View® Portable Infrared Boiler Thermometer is a handheld sensor that gives customers the ability to take temporary readings at various locations to ensure proper heat transfer and operation of emissions control systems. Our Infra-View® pyrometers can ensure durable designs, long-term dependability, and versatile options, capable of optimizing any applicable industrial process.

Use our Pyrometer Selector to find the right solution for your temperature monitoring needs and place a request for quote.

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