WHY BUY PRIMARY STANDARDS FROM HART? 

Setting up a primary temperature standards lab is no small project. Decisions must be made about temperature range, uncertainty requirements, the types of standards you need, and the companies that can supply your standards. Whose products are reliable? Which company backs up its performance claims? Who provides after-sale support and training? Who really demonstrates the most integrity throughout your ownership experience? After all, substantial investments are being made, and in many cases the credibility of your lab can be affected by the outcome. 

So why does Hart Scientific claim to be the world’s best supplier of primary temperature standards? Because our products have been tested over and over again by national labs around the world and proven to outperform their specs. Because the people who design and build primary temperature standards at Hart have been designing and building primary temperature standards longer than any other supplier in the world. We not only manufacture primary standards, we perform basic research and innovate with new primary standards designs. No other company offers the high-quality training and post-sale support that we do. No one! 

Metal Fixed-Point Cells 

For realizing the ITS-90 temperature scale, Hart’s metal fixed-point cells provide performance you can trust, and we supply the data with each cell to prove it. Hart’s fixed-point cells benefit from more than 20 years of experience in research, design, and manufacturing. Four types of cells are available: traditional size cells, “mini” quartz cells, new “mini” metal-cased cells, and small stainless steel “X” cells. All four provide outstanding performance. 

Each Hart cell is carefully assembled, tested, and supplied with an assay of metal-sample purity.  Every traditional size cell further undergoes more rigorous testing to a CCT-based procedure in our NVLAP-accredited lab, where we realize at least three freezing curves and perform a detailed “slope analysis” to confirm cell purity.  If you’d like this more thorough “slope analysis” for a “mini” quartz, new “mini” metal-cased, or small stainless steel “X” cells, we offer that as an option. And if you still want more, we can also supply comparison data with our own reference cells that have been independently tested at NIST. 

No other commercial company has as much experience in the development of fixed-point cells as Hart. Hart’s own Xumo Li was a key contributor to the development of the ITS-90 scale. That’s one reason you’ll find Hart cells in many of the national metrology institutes around the world. 

Water Triple Point Cells 

Like our metal fixed-point cells, Hart’s triple point of water cells come in traditional and “mini” quartz sizes as well as small stainless steel, which can be realized in a dry-well calibrator. Our traditional cells have been tested at NIST and are within a few micro-Kelvin of NIST’s cells. 

If you’re new to primary temperature standards and are considering a water triple point cell, one of our cells is sure to meet your requirements. We offer training through our seminars, insurance for our glass cells, and our stainless steel cell just can’t be broken! 

Maintenance Apparatus 

Maintaining fixed-point cells requires high-stability apparatus with tight gradient control so plateaus last longer and your work is more productive. Every Hart maintenance apparatus, including our metrology furnaces and fluid calibration baths, uses temperature controllers designed and manufactured by Hart. These controllers are widely recognized for their unmatched stability and uniformity control. 

For metal fixed-point cells, choose from one-zone, three-zone, or heat-pipe furnaces for regular or mini cells. Optional equilibration blocks fit into the furnaces for annealing and comparison calibrations. Don’t let the competition try to tell you that a furnace fitted with process controllers can provide the same performance as a furnace fitted with controllers designed specifically for high-stability temperature control. With a Hart furnace you’ll get longer cell plateaus with smaller gradients than you will from any other furnace on the market. 

SPRTs 

SPRTs are the only acceptable ITS-90 interpolation devices from the triple point of hydrogen (13.8033 K) to the freezing point of silver (961.78°C). While most SPRT manufacturers lost their design capabilities years ago, Hart continues to develop new innovative designs with the lowest drift rates. 

Hart manufactures quartz SPRTs in four different temperature ranges, including capsule SPRTs for low temperatures, an ultra-stable SPRT for the range to 480°C, and a new “working-standard” SPRT for the range to 660°C.  Our metal-sheath SPRTs include a 25.5-ohm, contamination-resistant SPRT, so you finally have a choice of suppliers. Hart SPRTs are the standards of choice for many national metrology institutes around the world. 

Thermometry 

Traditionally, SPRT measurements have been made using expensive, difficult-to-use resistance ratio bridges with typical ratio accuracies of 0.1 ppm (0.000025 °C). New technology in the Fluke Super-Thermometer from Hart Scientific makes primary standards level work much easier on metrologists and their budgets.

The accuracy of the 1595A at the triple point of water is 0.06 ppm (0.000015 °C; k = 2). And for common SPRT thermometry ratios up to 4:1, the 1595A's ratio accuracy is 0.2 ppm (0.00005 °C; k = 2).

Not only is overall measurement uncertainty effectively equal between the Super-Thermometer and a bridge, but the Super-Thermometer can make an accurate measurement ten times faster than a bridge, can calibrate itself with the patent-pending Ratio Self-Calibration function, and includes a multitude of time-saving features that simplify the calibration process.

Training 

Once you’ve determined which primary standards products you need and you’ve made a major investment, what about training and after-sales support? Hart’s temperature school offers a fun and unique seminar that provides all the answers to your toughest questions. If you want more, talk to us about onsite training. 

We’ve been making and using primary temperature standards for many years, and we understand the issues you face in your lab. Our own lab is accredited (NVLAP lab code 200348-0) and our uncertainties are among the best in the world. When you buy primary standards, don’t compromise the quality of the products, the reputation of your supplier, or the level of service and training they can provide. 

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