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<p>A new adiabatic calorimeter of free cryogens has been developed by the thermal metrology laboratory at National Institute of Standards NIS-Egypt. It can measure temperatures from 6.5 to 273&#xa0;K according to the International Temperature Scale of 1990 (ITS-90). The calorimeter has a closed-cycle Gifford–McMahon refrigerator that cools it down, and three thermal shields and two vacuum chambers that reduce parasitic heat flux transfer. The adiabatic chamber inside can hold either a cell with multiple compartments that has the triple points of oxygen and argon for measuring temperatures from 54 to 84&#xa0;K, or a block for comparing thermometers and calibrating capsule standard platinum resistance thermometers (CSPRTs) from 6 to 273&#xa0;K. The calorimeter uses a computer-controlled system and can run for a long time with good temperature control; this lowers the measurement errors significantly. NIS tested the new adiabatic calorimeter and confirmed its performance. The uncertainties in measuring temperatures according to the ITS-90 have been 1.72&#xa0;mK for the oxygen triple point and 1.68&#xa0;mK for the argon triple point. The system demonstrates significant improvements over previous designs by extending the operational temperature range down to 6&#xa0;K. Long-term temperature stability (with a plateau duration of approximately ~ 43&#xa0;h) and reproducibility have been validated using heat pulse techniques. The calorimeter's performance was characterized based on three key thermal parameters: the heat capacity of the cells, both with a copper block for comparison, the thermal resistance of the shield, and the recovery time following an intermittent heat pulse, as well as the precision of temperature control.</p>

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New adiabatic calorimeter for calibrating capsule standard platinum resistance thermometer in low-temperature fixed point at NIS-Egypt

  • 期刊论文

  • 发表日期：

    2025年8月30日

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  • A. El-Matarawy,
  • Mohamed Gamal Ahmed,
  • Doaa. M. Abdelgalil

摘要

A new adiabatic calorimeter of free cryogens has been developed by the thermal metrology laboratory at National Institute of Standards NIS-Egypt. It can measure temperatures from 6.5 to 273 K according to the International Temperature Scale of 1990 (ITS-90). The calorimeter has a closed-cycle Gifford–McMahon refrigerator that cools it down, and three thermal shields and two vacuum chambers that reduce parasitic heat flux transfer. The adiabatic chamber inside can hold either a cell with multiple compartments that has the triple points of oxygen and argon for measuring temperatures from 54 to 84 K, or a block for comparing thermometers and calibrating capsule standard platinum resistance thermometers (CSPRTs) from 6 to 273 K. The calorimeter uses a computer-controlled system and can run for a long time with good temperature control; this lowers the measurement errors significantly. NIS tested the new adiabatic calorimeter and confirmed its performance. The uncertainties in measuring temperatures according to the ITS-90 have been 1.72 mK for the oxygen triple point and 1.68 mK for the argon triple point. The system demonstrates significant improvements over previous designs by extending the operational temperature range down to 6 K. Long-term temperature stability (with a plateau duration of approximately ~ 43 h) and reproducibility have been validated using heat pulse techniques. The calorimeter's performance was characterized based on three key thermal parameters: the heat capacity of the cells, both with a copper block for comparison, the thermal resistance of the shield, and the recovery time following an intermittent heat pulse, as well as the precision of temperature control.