  We investigate the real-time estimation protocols for the frequency shift of
optically detected magnetic resonance (ODMR) of nitrogen-vacancy (NV) centers
in nanodiamonds (NDs). Efficiently integrating multipoint ODMR measurements and
ND particle tracking into fluorescence microscopy has recently demonstrated
stable monitoring of the temperature inside living animals. We analyze the
multipoint ODMR measurement techniques (3-, 4-, and 6-point methods) in detail
and quantify the amount of measurement artifact owing to several systematic
errors derived from instrumental errors of experimental hardware and ODMR
spectral shape. We propose a practical approach to minimize the effect of these
factors, which allows for measuring accurate temperatures of single NDs during
dynamic thermal events. We also discuss integration of noise filters, data
estimation protocols, and possible artifacts for further developments in
real-time temperature estimation. The present study provides technical details
of quantum diamond thermometry and discusses factors that may affect the
temperature estimation in biological applications.
