Case Study: National Physical Laboratory achieves reduced thermometer calibration uncertainty with COMSOL Multiphysics

Researchers are using simulation to improve calibration of temperature sensors

The National Physical Laboratory (NPL) in Teddington, UK, faced the challenge of understanding and reducing uncertainty in calibration of platinum resistance thermometers against the ITS-90 fixed points, where remaining uncertainty can be on the order of 1 millikelvin. To probe the microscopic behavior of freezing in fixed-point cells and the sensor reading, NPL researchers turned to Comsol, using the COMSOL Multiphysics simulation platform.

Using Comsol Multiphysics and a phase-field modeling approach, the team simulated solidification in the graphite fixed-point cell and revealed morphological instabilities—ripples and cellular protrusions at the liquid–solid interface whose tips were significantly colder than their roots. These insights identified previously hidden contributors to the ~1 mK calibration uncertainty, showed how furnace settings and heat/mass flow influence measurements, and provided a validated model to guide redesigns that can improve measurement precision.

National Physical Laboratory

Jonathan Pearce

Leads Contact Thermometry