Freeze
Point Cells - Temperature
Calibration - Primary Standards
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Freeze
Point Cells - Temperature
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| Freeze Point Cells - Temperature Calibration - Primary Standards from Hart Scientific |
| Metal Freeze Point Cells |
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Features |
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Assigned Value of Equilibrium Temperature (°C) |
Temperature
with Pressure, |
Variation
with Depth |
Correction for the Hydrostatic Head (mK) |
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5904 |
Indium (In) |
156.5985 |
4.9 |
3.3 |
+0.59 |
0.15–0.3 |
0.5–1.0 |
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5905 |
Tin (Sn) |
231.928 |
3.3 |
2.2 |
+0.40 |
0.2–0.4 |
0.7–1.4 |
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5906 |
Zinc (Zn) |
419.527 |
4.3 |
2.7 |
+0.49 |
0.2–0.4 |
0.8–1.6 |
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5907 |
Aluminum (Al) |
660.323 |
7.0 |
1.6 |
+0.29 |
0.6–1.0 |
2.5–5.0 |
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5908 |
Silver (Ag) |
961.78 |
6.0 |
5.4 |
+0.97 |
1.0–2.0 |
3.5–7.0 |
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5910 |
Gold (Au) |
1064.18 |
6.1 |
10 |
+1.8 |
1.0–2.0 |
4.0–8.0 |
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5909 |
Copper (Cu) |
1084.62 |
3.3 |
2.6 |
+0.47 |
2.0–4.0 |
7.0–15 |
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†The expanded uncertainty was evaluated to be at a level of two times the combined standard uncertainties. |
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Hart’s
scientists have designed and tested Metal Freeze Point Cells for many years.
We know how to make them and we know how to measure their absolute performance
in our laboratory before you use them.
Hart cells are made from very dense, high-purity graphite machined to form a crucible to contain the pure metal sample. These canisters are enclosed in a sealed quartz or borosilicate glass envelope. Hart uses metal samples certified to a purity of 99.9999% or higher. This is referred to as six 9s purity.
All parts used to construct the cells are subjected to high-temperature and high-vacuum treatment just prior to being filled with the metals. After assembly, the cell is connected to a vacuum system and pumped for several days. It is then purged with pure argon many times before sealing.
A special technique is used to seal the cell just at the freezing point. This way we can measure and record the pressure of the argon in the cell right at the freezing point, resulting in the smallest possible correction for pressure.
Everything important in the manufacturing of Freeze Point Cells has been studied and refined. Radiation losses along the well have been accounted for, possible stem error has been minimized, and pressure corrections have been made for precision cell construction. Hart cells are used in national metrology laboratories all over the world.
If you want information on the measurement stability of our cells over time, we’ll give you copies of our research and answer any questions you have. And if you would like, please visit our lab to do some hands-on calibrations with the cells of your choice. See how they perform under laboratory conditions, and learn how to create and maintain the longest freeze plateaus in the industry.
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