How to calibrate a temperature sensor | Comparative calibration vs. fixed-point calibration
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5 سال پیش
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For the calibration of temperature
For the calibration of temperature measuring instruments such as dial thermometers, resistance thermometers (e.g. Pt100/Pt1000) or thermocouples, there are two methods: fixed-point calibration or comparative calibration (https://bit.ly/2RkEqbS).
🎯 Fixed-point calibration
The uniqueness of the triple point provides particularly good temperature fixed points for calibration. In thermodynamics, the triple point (also three-phase point) is the condition in which three aggregate states of a substance are in thermodynamic equilibrium. For water, for example, this triple point, according to the international temperature scale from 1990 (ITS-90), is exactly 0.01 °Celsius. This means that the quantitative ratio of water in the liquid phase, steam and ice does not change. As a consequence of this, all three phases co-exist simultaneously.
It is time-consuming and complex to reach the triple point, but once it is reached, the temperature remains stable over a longer period of time. At this constant temperature, the most exact check of the deviation of the temperature probe can be made.
The fixed-point methodology is recommended for thermometers which have high requirements for reproducibility and accuracy, especially if these measuring instruments are used as reference thermometers.
🎯 Comparative calibration
With this calibration method, measured values of the calibration item are compared with a reference thermometer. The comparative calibration is carried out in a calibration bath, a calibration block or a tube furnace. For this, the temperature probe is introduced into the test instrument and the deviation of the test item from the reference thermometer is documented at different measuring points. Through the traceability of the reference thermometer, different levels of accuracy can be made possible.
The measurement uncertainties with comparative calibration are, however, always higher than in a calibration using the fixed-point methodology. The comparative method is thus often used in industrial temperature measurement. Here a balance between the accuracy, time and traceability of the measuring result is important.
In its traceable and accredited calibration laboratories, WIKA uses comparative calibration and also calibration at six fixed points. WIKA's calibration service is available worldwide and even offers a quick and uncomplicated in-house service. https://bit.ly/3QgvzDJ
Learn more on the WIKA blog about:
📖 Comparative calibration vs. fixed-point calibration: https://bit.ly/2YhAUAB
📖 Calibrating thermometers – an overview: https://bit.ly/2OS5opv
📖 Operation of a temperature dry-well calibrator: https://bit.ly/2DL0hkI
You may also be interested in these videos:
▶ Factory calibration vs. traceable DAkkS calibration to ISO 17025 | What is the difference? Factory calibration vs. traceable cal...
▶ Bimetal vs. gas-actuated thermometers | What is the difference? Bimetal vs. gas-actuated thermometers...
▶ How does a resistance thermometer work? | Resistance thermometers per IEC 60751 How does a resistance thermometer wor...
▶ How does a thermocouple work? | Thermocouples per IEC 60584-1 and ASTM E230 Thermocouple basic working principles...
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Follow us on our social media channels:
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▬ Contents of this video ▬▬▬▬▬▬▬▬▬▬▬▬
0:00 Intro
0:08 Calibration options for temperature measuring instruments
0:18 Fixed points calibration
0:24 Triple point of water
0:54 Fixed point method suitability
1:06 Comparison calibration
1:42 Comparison method suitability
1:53 WIKA's traceable and accredited laboratory
🎯 Fixed-point calibration
The uniqueness of the triple point provides particularly good temperature fixed points for calibration. In thermodynamics, the triple point (also three-phase point) is the condition in which three aggregate states of a substance are in thermodynamic equilibrium. For water, for example, this triple point, according to the international temperature scale from 1990 (ITS-90), is exactly 0.01 °Celsius. This means that the quantitative ratio of water in the liquid phase, steam and ice does not change. As a consequence of this, all three phases co-exist simultaneously.
It is time-consuming and complex to reach the triple point, but once it is reached, the temperature remains stable over a longer period of time. At this constant temperature, the most exact check of the deviation of the temperature probe can be made.
The fixed-point methodology is recommended for thermometers which have high requirements for reproducibility and accuracy, especially if these measuring instruments are used as reference thermometers.
🎯 Comparative calibration
With this calibration method, measured values of the calibration item are compared with a reference thermometer. The comparative calibration is carried out in a calibration bath, a calibration block or a tube furnace. For this, the temperature probe is introduced into the test instrument and the deviation of the test item from the reference thermometer is documented at different measuring points. Through the traceability of the reference thermometer, different levels of accuracy can be made possible.
The measurement uncertainties with comparative calibration are, however, always higher than in a calibration using the fixed-point methodology. The comparative method is thus often used in industrial temperature measurement. Here a balance between the accuracy, time and traceability of the measuring result is important.
In its traceable and accredited calibration laboratories, WIKA uses comparative calibration and also calibration at six fixed points. WIKA's calibration service is available worldwide and even offers a quick and uncomplicated in-house service. https://bit.ly/3QgvzDJ
Learn more on the WIKA blog about:
📖 Comparative calibration vs. fixed-point calibration: https://bit.ly/2YhAUAB
📖 Calibrating thermometers – an overview: https://bit.ly/2OS5opv
📖 Operation of a temperature dry-well calibrator: https://bit.ly/2DL0hkI
You may also be interested in these videos:
▶ Factory calibration vs. traceable DAkkS calibration to ISO 17025 | What is the difference? Factory calibration vs. traceable cal...
▶ Bimetal vs. gas-actuated thermometers | What is the difference? Bimetal vs. gas-actuated thermometers...
▶ How does a resistance thermometer work? | Resistance thermometers per IEC 60751 How does a resistance thermometer wor...
▶ How does a thermocouple work? | Thermocouples per IEC 60584-1 and ASTM E230 Thermocouple basic working principles...
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Follow us on our social media channels:
📺 YouTube: wikagroup
🎯 LinkedIn: LinkedIn: wikagroup
▬ Contents of this video ▬▬▬▬▬▬▬▬▬▬▬▬
0:00 Intro
0:08 Calibration options for temperature measuring instruments
0:18 Fixed points calibration
0:24 Triple point of water
0:54 Fixed point method suitability
1:06 Comparison calibration
1:42 Comparison method suitability
1:53 WIKA's traceable and accredited laboratory
5 سال پیش
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