ITS-90 Fixed-Point Cells

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Key features

  • Constructed using metal samples with purity of at least 99.9999 % (six 9s) and, in many cases, 99.99999 % (seven 9s).
  • Every ITS-90 fixed point available from argon to copper
  • Plateaus last days (gallium for weeks and TPW for months).
  • Accredited Cell Intercomaparisons available.

Product overview: ITS-90 Fixed-Point Cells

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Traditional freeze-point cells

If you want true primary temperature standards capability, you want metal freeze-point cells that are very close to the theoretical freezing temperature and provide plateaus that are both stable and long lasting.

Fluke Calibration's metal freeze-point cells are the culmination of more than 20 years of primary standards experience. No other company has as much experience in the development of metal fixed-point cells. That’s why you’ll find Fluke cells in many national metrology institutes around the world.

Each Fluke Calibration cell is carefully constructed in our ultra-clean, state-of-the-art lab, using high-density, high-purity graphite crucibles containing metal samples with purity of at least 99.9999 % (six 9s) and, in many cases, 99.99999 % (seven 9s). The crucible is enclosed within a sealed quartz glass envelope that is evacuated and back-filled with high-purity argon gas. A special sealing technique is used to seal the cell at the freezing point. We measure and record for you the precise pressure of the argon gas to ensure the most accurate corrections for pressure.

Once manufactured, all Fluke cells are tested and supplied with an assay of metal-sample purity. Every traditional size ITS-90 cell further undergoes more rigorous testing in our primary standards lab where we realize melt-freeze curves and perform a detailed “slope analysis" to confirm cell purity. If you want more data, we’ll give you an optional intercomparison with our own reference cells.

Gallium cells

Gallium cells are a great reference for validation of instruments subject to drift (like SPRTs), and they’re important for calibrating sensors used near room or body temperatures, in environmental monitoring, and in life sciences applications.

Fluke Calibration's 5943 Gallium Cell is sealed in a stainless steel envelope. High purity gallium (99.99999 %) is enclosed in a plastic and metal shell. The stainless steel container is then filled with pure argon gas at one standard atmosphere at the melting-point temperature.

Gallium expands by 3.1 % when it freezes requiring the cell to have flexible walls. Unlike some manufacturers’ cells, which are made from PTFE enclosure materials, our cells don’t need pumping and refilling because they’re not gas permeable. In fact, we guarantee our cells will maintain their uncertainty of < 0.1 mK for at least five years. Realization and maintenance of the cell is automated with our 9230 Maintenance Apparatus (see page 31). This apparatus will provide melting plateaus up to eight days and a convenient control to automatically achieve a new melt plateau each week with an investment of just five minutes. Never has the maintenance of a world-class gallium cell been easier.

Water cells

While simple ice baths are often used as a calibration point at 0 °C, their limitations include gradients, purity problems, repeatability issues, and variances in construction and measurement techniques. Triple point of water cells not only solve these problems; they represent the most used temperature on the ITS-90, and they’re inexpensive to own and use.

Fluke Calibration makes three traditional-size TPW cells that have been repeatedly proven in national labs to surpass their published uncertainty specification of ±0.0001 °C. Ice mantles may be formed using dry ice, LN2 , or immersion freezers and can last for up to two months when maintained in our 7012 or 7312 baths.

Open metal cells

Made from the same materials and with the same manufacturing techniques as their sealed counterparts, Fluke's new series of “open" metal fixed-point cells include a high quality valve for connecting to a precision pressure-handling system within your lab. Using such a system, the cell can be evacuated, charged, and purged several times with a pure inert gas, then charged again to a regulated pressure level while measurements are made with the cell.

Once assembled and tested, each Fluke Calibration ITS-90 open cell further undergoes more rigorous testing in our lab, unlike cells from some manufacturers who provide their open cells as a kit of parts, without any test data.

Because open cells allow users to measure the pressure within the cell, uncertainties due to pressure corrections may be minimized. Use of open cells is now being suggested by the CCT, and open cells can be used for demanding temperature-versus-pressure applications, as well as precision SPRT calibrations.

The height of these cells has been extended to allow easy access to the gas valve while the cells are in use. Pure quartz-wool insulation and four high-purity graphite discs prevent heat loss from the metal sample to the pressure regulation system while optimizing vertical temperature gradients within the cell. Each cell has an outside diameter of 50 mm (2 inches) and a height of 600 mm (23.5 inches)—(silver and copper cells are 700 mm [27.6 inches] tall).

When it comes to primary temperature standards, Fluke Calibration supplies more equipment than all of our competitors combined. If your goal is to reduce uncertainty, start by buying from the company that supports its products better than any other metrology company in the world. Why trust your primary standards to any other company?

Specifications: ITS-90 Fixed-Point Cells

Specifications
ModelFixed PointStyleAssigned Value ( °C)Outside DiameterInside DiameterTotal Outside Cell HeightDepthCell Uncertainty (mK, k=2)Certification (mK, k=2)
5900EMercuryStainless Steel–38.834431 mm8.2 mm470 mm200 mm0.20.25
5904IndiumTraditional Quartz Glass156.598548 mm8 mm285 mm195 mm0.70.7
5905TinTraditional Quartz Glass231.92848 mm8 mm285 mm195 mm0.50.8
5906ZincTraditional Quartz Glass419.52748 mm8 mm285 mm195 mm0.91.0
5907AluminumTraditional Quartz Glass660.32348 mm8 mm285 mm195 mm1.31.8
5908SilverTraditional Quartz Glass961.7848 mm8 mm285 mm195 mm2.44.5
5909CopperTraditional Quartz Glass1084.6248 mm8 mm285 mm195 mm10.112.0
5924IndiumOpen Quartz Glass156.598550 mm8 mm596 mm195 mm0.70.7
5925TinOpen Quartz Glass231.92850 mm8 mm596 mm195 mm0.50.8
5926ZincOpen Quartz Glass419.52750 mm8 mm596 mm195 mm0.91.0
5927A-LAluminumOpen Quartz Glass (long)660.32350 mm8 mm696 mm195 mm1.31.8
5927A-SAluminumOpen Quartz Glass (short)660.32350 mm8 mm596 mm195 mm1.31.8
5928SilverOpen Quartz Glass961.7850 mm8 mm696 mm195 mm2.44.5
5929CopperOpen Quartz Glass1084.6250 mm8 mm696 mm195 mm1012.0
5943GalliumStainless Steel29.764638.1 mm8.2 mm250 mm168 mm0.10.1
Certification uncertainty values may vary slightly from those listed here. If the exact value is needed, please contact Fluke.
Depth is measured from the bottom of the thermometer well to the top of the pure reference material.

Models: ITS-90 Fixed-Point Cells

5900E
Mercury Triple Point Cell, Stainless Steel

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5904
Indium Cell, Traditional Quartz Glass

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5905
Tin Cell, Traditional Quartz Glass

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5906
Zinc Cell, Traditional Quartz Glass

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5907
Aluminum Cell, Traditional Quartz Glass

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5908
Silver Cell, Traditional Quartz Glass

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5909
Copper Cell, Traditional Quartz Glass

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5924
Indium Cell, Open Quartz Glass

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5925
Tin Cell, Open Quartz Glass

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5926
Zinc Cell, Open Quartz Glass

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5927A-L
Aluminum Cell, Open Quartz Glass, Long

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5927A-S
Aluminum Cell, Open Quartz Glass, Short

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5928
Silver Cell, Open Quartz Glass

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5929
Copper Cell, Open Quartz Glass

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5943
Gallium Cell, Metal Cased

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1904-Ag

Accredited Cell Intercomparison, Silver


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1904-In

Accredited Cell Intercomparison, Indium


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1904-Sn

Accredited Cell Intercomparison, Tin


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1904-Zn

Accredited Cell Intercomparison, Zinc


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1904-Al

Accredited Cell Intercomparison, Aluminum


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Manuals + resources: ITS-90 Fixed-Point Cells