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Relation Between Wire Resistance and Fluid Pressure in the Transient Hot-Wire Method.
1National Institute of Standards and Technology, Boulder, CO 80303.
Summary
Metal resistance changes significantly with applied pressure. For accurate thermal conductivity measurements, calibrate instruments in situ or use a specific pressure correction factor for platinum wires.
Area of Science:
- Materials Science
- Physics
- Metrology
Background:
- The electrical resistance of metals is known to be pressure-dependent.
- This pressure dependence can impact the accuracy of scientific instruments relying on resistance measurements.
Purpose of the Study:
- To quantify the pressure dependence of metal resistance.
- To assess the significance of this effect on transient hot-wire thermal conductivity instruments.
- To provide recommendations for improving calibration accuracy.
Main Methods:
- Investigated the relationship between applied pressure and the electrical resistance of metals.
- Focused on platinum, a common material for hot-wire sensors.
- Analyzed the impact of pressure-induced resistance changes on thermal conductivity measurements.
Main Results:
- The pressure dependence of metal resistance is significant for instrument calibration.
- A relative resistance change with pressure (γ) of -2×10⁻⁵ MPa⁻¹ was determined for platinum.
- This effect must be considered for accurate thermal conductivity measurements.
Conclusions:
- In situ calibration of hot-wire sensors is recommended for highest accuracy.
- If in situ calibration is not feasible, a correction factor for pressure dependence should be applied.
- Accurate calibration is crucial for reliable thermal conductivity data.
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