Precise temperature measurement at 30Â K in the KATRIN source cryostat

► Temperature measurement at 30 K and 3.6 T with accuracy requirements better 0.1% and with operating temperatures up to 550 K. ► Dispersion, stability and magnetic field behaviour of Pt500 sensors. Standard uncertainties at 30 K and 120 K. ► Vapour pressure sensor development with liquid nitrogen measurements. Estimated standard uncertainty with neon at 30 K. ► Pt500 in situ calibration with vapour pressure sensors.