Groups are used, if the relative deviation between sensors must be in the range of 50 mK to 100 mK but the absolute accuracy might be higher (e.g. according to IEC 60751 F0.3). IST AG sorts the sensors at the final measurement in different groups according to the customer requirements. The customer benefits that all sensors within a group meet the tight relative tolerance but keeps the price benefit of a wider tolerance class. Customer-specific designed sensors benefit from this technique.
Pairs are used in applications, where two sensors should have virtually no deviation between each other. IST AG sorts the sensors after the final measurement in such a way, that the two most similar sensors in terms of R0 and temperature characteristics are packaged together–taking into account the maximum allowed deviations given by the customer. In many cases this helps eliminate, or at least reduce the calibration efforts by the customer.