Since 1995 Isotech have been producing various designs of special Pt/Au, Pt/Pd, Pd/Au thermocouples for
researchers. From our experience we can now offer the most popular of these, the Pt/Au thermocouple in
a standard form.
All wires are 99.999+% pure and are fully annealed according to the recommendations of McLaren
Assembly also follows his prescriptions which have never been bettered.
After final assembly and annealing the Pt/Au thermocouples will conform to the reference function derived
by Burns within ±0.05°C.
For smaller uncertainties we calibrate the thermocouple at the Tin, Zinc, Aluminum and Silver Fixed Points.
The associated uncertainties being Zinc ±2.5mK, Aluminium±4mK and Silver ±6mK (1 sigma). The
reproducibility of the thermocouples is less than ±0.05°C.
We achieve these results because:
1. All materials are selected for their purity and high quality.
2. All parts are pre-aged and annealed prior to construction.
3. The construction allows for differential expansion of the Gold and the Platinum by having a coil of
platinum bridge the two thermo elements at their measuring junction.
4. There are no joins between the measuring and reference junctions.
5. The reference junction is also researched and we use thermally pure copper wire of selected diameter
which has been pre-annealed in inert gas to maintain the accuracy of the measuring junction.
6. The reference junction needs to be placed in an accurate reference system such as a Water Triple Point
Cell or an Isotech Zeref.
7. An article describing in detail the construction, handling and operation of the thermocouple is provided
free with each unit.
Semi-Standard Thermocouple Product Spec Sheet
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