Extensions of Callendar's equations for platinum resistance thermometry

Callendar's equations are generalized to permit interpolation between arbitrary fixed points. Fixed points appropriate to a desired temperature region may thus be employed rather than Callendar's fixed 0 and 100°C calibration points. This should afford greater accuracy, especially in industrial measurements where the platinum thermometer and the measurement means may be less than ideal.

To this end. Callendar's definition of platinum temperature is generalized to mean the temperature found by linear interpolation with a platinum thermometer between given fixed points and using a given measurement method. The true temperature may then be found either by recursion or by an extension of Callendar's correction scheme