Having the fundamentals in mind makes it easier to understand the factors that can affect the accuracy of thermocouple If any of these variables are unknown, the temperature at the thermocouple sensing junction cannot be determined.Įquation 2 shows an updated calculation for measuring the temperature at the hot junction of a thermocouple, taking the above parameters into account:Ī(T c): Seebeck coefficient as a function of T c in µV/☌ Factors that Impact Accuracy of Thermocouple Readings The thermoelectric voltage due to thermal gradient between the hot and cold junctions.The following three parameters must be known: Understand that a temperature measurement cannot be determined solely from the EMF generated by the thermocouple. Modern thermocouple measurement techniques should take this non-linearity into account. Using a linear approximation of the Seebeck effect can produce significant measurementĮrrors. Non-linear dependence on the temperature. The Seebeck coefficient is specific to the two conductors that are used to construct the thermocouple. T h - T c: Temperature difference between hot and cold junctions S: Seebeck coefficient in V/K (commonly in µV/☌) ÆV: Voltage difference between two dissimilar metals Seebeck effect, which describes the voltage that results from the thermocouple materials and the temperature difference between the hot and cold junctions.Įquation 1 provides a linear approximation of the Seebeck effect. EMF is measured in the millivolts range and is the product of a physical phenomenon known as the Maintaining the two junctions at different temperatures produces an electromotive force (EMF), also known as the How Thermocouples Are CreatedĪ combination of two dissimilar conductors forming "hot" and "cold" junctions creates a thermocouple (Figure 1). Providing an understanding that will help readers improve the accuracy of their readings. This application note examines how thermocouples are constructed and the physics behind how they work, However, as is also commonly the case with many types of sensors, acquiring accurate data with thermocouplesĬan be challenging. Thermocouples are a common type of temperature sensor used in applications ranging from lab test benches to industrialĮnvironments. If you do not allow these cookies, you will experience reduced relevant content.This application note examines how thermocouples are constructed and the physics behind how they work, providing readers with an understanding that will help them improve the accuracy of thermocouple readings. They do not store directly personal information, but are based on uniquely identifying your browser and internet device. They may be used by Analog Devices to build a profile of your interests and show you relevant content on our site. Targeting Cookies: These cookies may be set through our site by Analog Devices and our service providers. If you do not allow these cookies we will not know when you have visited our site, and will not be able to monitor its performance. All information these cookies collect is aggregated and therefore anonymous. They help us to know which pages are the most and least popular and see how visitors move around the site. Performance Cookies: These cookies allow us to count visits and traffic sources so we can measure and improve the performance of our site. If you do not allow these cookies then some or all of these services may not function properly. They may be set by us or by third party providers whose services we have added to our pages. Functional Cookies: These cookies enable the website to provide enhanced functionality and personalization. These cookies do not store any personally identifiable information. You can set your browser to block or alert you about these cookies, but some parts of the site will not then work. They are usually only set in response to actions made by you which amount to a request for services, such as setting your privacy preferences, logging in or filling in forms. Strictly Necessary Cookies: (Always Active) These cookies are necessary for the website to function and cannot be switched off in our systems. After we finish updating our website, you will be able to set your cookie preferences. Analog Devices is in the process of updating our website.
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