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Calibration of ITS-90 Defining Artifacts

The Standard Platinum Resistance Thermometer Calibration Laboratory (SPRTL) realizes the ITS-90 using fixed-point cells from the Ar TP (–189.3442 °C) to the Ag FP (961.78 °). Calibration and certification services are provided for the following ITS-90 defining artifacts:

  • Standard platinum resistance thermometers
  • Fixed-point cells

Additional specialized services (e.g. proficiency-test artifacts, bridge certification) can be found on the Special Tests for Thermometry webpage.

The Low Temperature Calibration Facility (LTCF) Cryogenic Thermometer Calibration Laboratory calibrates thermometers from 0.5 K to 165 K. Information for these calibrations are found on the Cryogenic Thermometer Calibration Laboratory webpage.

How to Arrange a Calibration

  • Contact the staff member in charge of the calibration service for your artifact with any technical or calibration cost questions.
  • Calibrations are performed on a first come first serve basis.
  • Ship your artifact with a copy of the purchase order. Use a sturdy box in which we can return the calibrated instrument.
  • SPRT Calibration Customers: Please provide the most recent R(TPW) value measured with your device, if applicable. This allows us to determine whether any changes occurred during shipping.
  • The purchase order may be sent to contact by e-mail, fax, or mail. Please include the following information:
    • service ID for the calibration
    • model and serial number of your artifact
    • customer contact name, address, phone, and e-mail
    • return shipping method (e.g., shipping account number)

For contact information, shipping address, or cost of calibration, see Resistance Thermometry.


Calibration Measurement Uncertainties


ITS-90 Fixed-Point Cells

Fixed-Point Cell

U (k=2), mK

Ar TP

0.14

Hg TP

0.15

Water TP

0.06

Ga TP

0.07

In FP

0.18

Sn FP

0.28

Zn FP

0.51

Al FP

0.79

Ag FP

1.21



ITS-90 Subranges

Temperature Range, °C

Maximum U (k=2), mK†

Ar TP to TPW

0.40

Hg TP to Ga MP

0.23

0 °C to Ga MP

0.07

0 °C to In FP

0.36

0 °C to Sn FP

0.48

0 °C to Zn FP

0.59

0 °C to Al FP

0.82

0 °C to Ag FP

1.95


† The ITS-90 temperature subrange uncertainties include the propagated fixed-point uncertainties and the contribution from non-uniqueness types I and III.