Thermocouple Accuracy and Noise?

In summary, the MAX31855 thermocouple-to-digital converter can measure temperatures in the range of 0-350C and has a 0.25C resolution regardless of the type of thermocouple used. There is no inherent advantage to one type of thermocouple over another in terms of accuracy or noise. The article provided has a discussion on each type of thermocouple, but the ADC in the MAX31855 should be adequate for all types.
  • #1
tangodirt
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I'm looking to use the MAX31855 thermocouple-to-digital converter, to measure temperatures in the range of 0-350C. According to the manufacturer, the ADC inside the chip is identical for every different type of thermocouple, just a different sensitivity is programmed in depending on the type of thermocouple you want to use. So, each chip, regardless of thermocouple type, outputs at a 0.25C resolution.

Therefore, since every type of thermocouple that the chip is trimmed for will read my range, is there any inherent advantage to one over another (K, J, N, T, S, R, and E)?

Specifically, are any (on average) more accurate than another? Do any of them have less inherent noise? Are there any advantages to one over another? Thanks!
 
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  • #2

1. What factors affect the accuracy of a thermocouple?

There are several factors that can affect the accuracy of a thermocouple, including the material used for the thermocouple wires, the homogeneity of the materials, the temperature range, and the junction type. Another important factor is the reference junction compensation, which is necessary to accurately measure the temperature difference between the hot and cold junctions.

2. How is the accuracy of a thermocouple determined?

The accuracy of a thermocouple is typically determined by comparing its output to a known temperature in a controlled environment. This is usually done using a calibration furnace or a precision thermometer. The accuracy can then be calculated by taking the difference between the measured temperature and the known temperature.

3. What is the typical accuracy of a thermocouple?

The accuracy of a thermocouple can vary depending on the type and quality of the thermocouple, as well as the temperature range it is being used in. Generally, the accuracy can range from ±0.5°C to ±2.5°C. It is important to note that the accuracy can also be affected by external factors such as electrical interference or corrosion of the wires.

4. How can noise affect the accuracy of a thermocouple?

Noise can have a significant impact on the accuracy of a thermocouple. This is because thermocouples produce a small voltage signal, which can be easily affected by electrical interference. High levels of noise can cause fluctuations in the voltage signal, leading to inaccurate temperature readings. To minimize noise, it is important to properly shield the thermocouple wires and ensure a good electrical connection at the junction.

5. What are some ways to improve the accuracy of a thermocouple?

There are several ways to improve the accuracy of a thermocouple, such as using a higher quality thermocouple with a smaller measurement error, properly calibrating the thermocouple, and reducing external noise sources. It is also important to ensure that the thermocouple is properly installed and maintained, as any damage or wear can affect its accuracy. Additionally, using a reference junction compensation technique can help improve the accuracy of the temperature measurement.

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