  The efficiencies of the spin-orbit torques (SOTs) play a key role in the
determination of the power consumption, integration density, and endurance of
SOT-driven devices. Accurate and time-efficient determination of the SOT
efficiencies is of great importance not only for evaluating the practical
potential of SOT devices but also for developing new mechanisms for enhancing
the SOT efficiencies. Here, we develop a "two-field-scan" harmonic Hall voltage
(HHV) analysis that collects the second HHV as a function of a swept in-plane
magnetic field at 45{\deg} and 0{\deg} relative to the excitation current. We
demonstrate that this two-field-scan analysis is as accurate as the
well-established but time-consuming angle-scan HHV analysis even in the
presence of considerable thermoelectric effects but takes more than a factor of
7 less measurement time. We also show that the 3-parameter fit of the HHV data
from a single field scan at 0{\deg}, which is commonly employed in the
literature, is not reliable because the employment of too many free parameters
in the fitting of the very slowly varying HHV signal allows unrealistic
pseudo-solution and thus erroneous conclusion about the SOT efficiencies.
