README.md

🌡 ITS-90 SPRT Calibration Data Format

ITS-90 Compact v1.0

This format is dedicated for QR Codes and URLs but can be used for any purpose.

File extension: .qt90

Formats:

Variant A:

qt90://[Sub-Range]/[Fixed point]_[Fixed point]/[Coefficient]_[Coefficient]

Variant B:

qt90://[Sub-Range]/[Fixed point]_[Fixed point]

Variant C:

qt90://[Sub-Range]/[Triple point of Water]/[Coefficient]_[Coefficient]

Sub-Range:

Integer identifier.

More at: Appendix A: ITS-90 Sub-ranges

Fixed points:

[Temperature(Kelvin)~Uncertainty(Kelvin)]K[Resistance(Ohms)~Uncertainty(Ohms)]

Notice how ± is represented by ~.

One can use one of the two notations:

• Temperatures

273.16~0.009K100.017~0.006

• Shorthand letters

W~0.009K100.0170~0.006

Notice how temperature is now replaced by one letter (for list of letters see Appendix B):

Uncertainty can be ommited for resistance:

273.16~0.009K100.017

Coefficients:

Format: [A]_[B]_[C]

Example:

-2.0786366E-04_-8.8309895E-05

Full example

Sub-Range 8: 0.01 °C to 419.527 °C (Water-Zinc)

Calibration points:

• Water: 273.16 ± 0.009K
  • Resistance: 100.0135 ± 0.006Ω
• Tin: 505.078 ± 0.012K
  • Resistance: 188.9427 ± 0.006Ω
• Zinc: 692.677 ± 0.096K
  • Resistance: 256.6981 ± 0.006Ω

Coefficients:

• a8: -2.0786366E-04
• b8: -8.8309895E-05

Calibration data:

Variant A:

• Temperatures

8/273.16~0.009K100.0135~0.006_505.078~0.012K188.9427~0.006_692.677~0.096K256.6981~0.006/-2.0786366E-04_-8.8309895E-05

• Shorthand letters:

8/W~0.009K100.0135~0.006_T~0.012K188.9427~0.006_Z~0.096K256.6981~0.006/-2.0786366E-04_-8.8309895E-05

Variant B:

8/W~0.009K100.0135~0.006_T~0.012K188.9427~0.006_Z~0.096K256.6981~0.006

Variant C:

8/W~0.009K100.0135/-2.0786366E-04_-8.8309895E-05

Full payload:

qt90://8/273.16~0.009K100.0135~0.006_505.078+0.012K188.9427~0.006_692,677~0.096K256.6981~0.006/-2.0786366E-04_-8.8309895E-05

As QR code:

Appendix A: ITS-90 Sub-ranges

Sub-Range 1:

-259.3467 °C to +0.01 °C

TP of Hydrogen to TP of Water

Sub-Range 2:

-248.5939 °C to +0.01 °C

TP of Neon to TP of Water

Sub-Range 3:

-218.7916 °C to +0.01 °C

TP of Oxygen to TP of Water

Sub-Range 4:

-189.3442 °C to +0.01 °C

TP of Argon to TP of Water

Sub-Range 5:

-38.8344 °C to +29.7646 °C

TP of Mercury to MP of Gallium

Sub-Range 6:

+0.01 °C to +961.78 °C

TP of Water to FP of Silver

Sub-Range 7:

+0.01 °C to +660.323 °C

TP of Water to FP of Aluminum

Sub-Range 8:

+0.01 °C to +419.527 °C

TP of Water to FP of Zinc

Sub-Range 9:

+0.01 °C to +231.928 °C

TP of Water to FP of Tin

Sub-Range 10:

+0.01 °C to +156.5985 °C

TP of Water to FP of Indium

Sub-Range 11:

+0.01 °C to +29.7646 °C

TP of Water to MP of Gallium

Appendix B: ITS-90 Fixed Points shorthand letters

• L - Freezing Point of Aluminum
• R - Triple Point of Argon
• G - Melting Point of Gallium
• H - Triple Point of Helium
• I - Freezing Point of Indium
• M - Freezing Point of Mercury
• N - Triple Point of Neon
• O - Triple Point of Oxygen
• S - Freezing Point of Silver
• T - Freezing Point of Tin
• W - Triple Point of Water
• Z - Freezing Point of Zinc