  The sharp microcanonical multifragmentation model from [Al. H. Raduta and Ad.
R. Raduta, Phys. Rev. C 55, 1344 (1997); Phys. Rev. C, in press] is employed
for evaluating the nuclear caloric curve predictions of nine isotopic
thermometers for three representative nuclei. Evaluations are performed for
both primary decay and asymptotic stages. Effects of the secondary decays on
the primary decay caloric curves are evidenced and discussed. In both cases a
dispersive character of the isotopic caloric curves with increasing the source
excitation energy is observed. A procedure of calibrating the isotopic
thermometers on the microcanonical predictions for both primary decay and
asymptotic stages is proposed. The resulting set of calibrating parameters for
each thermometer is independent on the source size, on its excitation energy
and, in the case of the primary decay, on the freeze-out radius assumption.
