  Velocity errors in particle tracking velocimetry (PTV) are studied. When
using high-speed video cameras, the velocity error may increase at a high
camera frame rate. This increase in velocity error is due to particle-position
uncertainty, which is one of two sources of velocity errors studied here. The
other source of error is particle acceleration, which has the opposite trend of
diminishing at higher frame rates. Both kinds of errors can propagate into
quantities calculated from velocity, such as the kinetic temperature of
particles or correlation functions. As demonstrated in a dusty plasma
experiment, the kinetic temperature of particles has no unique value when
measured using PTV, but depends on the sampling time interval or frame rate. It
is also shown that an artifact appears in an autocorrelation function computed
from particle positions and velocities, and it becomes more severe when a small
sampling-time interval is used. Schemes to reduce these errors are
demonstrated.
