SPRT is a standard which is used for defining temperature as per ITS-90. The ITS-90 extends defines upwards from 0.65 K to the highest temperature practicably measurable in terms of the Planck radiation law using monochromatic radiation.

The range from The Triple Point of Equilibrium Hydrogen (13.8033 K) to the Freezing Point of Silver (961.78°C) Platinum Resistance Thermometer is used as a defining sensor.

This SPRT calculator is used to provide the ITS-90 co-eficients for the set of resistance readings provided on the fixed point cell.

For the range 0°C to 961.78°C the following reference function is defined:



An inverse function, equivalent to equation (10a) to within 0.13 mK is Eq 10b

The values of the constants Co, Ci, Do and Di are given in Table 4.

A thermometer may be calibrated for use throughout this range or, using fewer calibration points, for ranges with upper limits of 660.323°C, 419.527°C, 231.928°C, 156.5985°C or 29.7646°C, all having a lower limit of 0°C.

Substance	Temp K	Temp °C	State
Water, H20	273.16	0.01C	Triple Point
Gallium, Ga	302.9146	29.7646	Melting Point
Indium, In	429.7485	156.5985	Freezing Point
Tin, Sn	505.078	231.928	Freezing Point
Zinc, Zn	692.677	419.527	Freezing Point
Aluminium, Al	933.473	660.323	Freezing Point
Silver, Ag	1234.93	961.78	Freezing Point

The free software has been specifically designed to provide the ITS90 parameters for temp range 0 to 660 deg C. For this the user has to provide the resiatnce values at TPW, FP Sn, FP Zn and FP of Al. The software shall calculate and provide the ITS90 coeficients and shall also generate a report for every 1 degree of interpolated readings for the sensors.

Other specific software for larger range can be provided on request.

This software is free of charge and can be distributed freely. It has been designed for the use at Tempsens, please double check before use. Tempsens stand no guarantee for the output. We are open to your feedback for improvement.