Modern technologies, e.g., scanning atomic force microscopy, accurate positioning systems for microchip fabrication and cell manipulation devices, demand accurate and precise mechanical displacement control, in the range from fractions of nanometers to tens of micrometers. Piezoelectric ceramics, such as PZT, can generate subnanometric displacements, but in order to generate multi-micrometric displacements, they should be either driven by high electric voltages (hundreds of volts), or operate at a mechanical resonant frequency (in narrow band), or have large dimensions (tens of centimeters). A multi-actuated piezoelectric actuator is a device with small dimensions that can be driven by reduced voltages and can operate in the nano/ micro scale. Interferometric techniques are very adequate for the characterization of these devices, because there is no mechanical contact in the measurement process, it has high sensitivity, bandwidth and dynamic range. A low cost open-loop homodyne Michelson interferometer is used in this work to experimentally detect the nanovibrations of XY actuators, based on the spectral analysis of the interferometric signal. A new phase demodulation method is proposed, which presents the following characteristics: is direct (no Bessel functions inversion), self-consistent (no external standard calibration), is immune to fading, and do not present phase ambiguity problems. The proposed method has resolution that is similar to the Modified J1...J4 method (0.18 rad); however, differently from the former, its dynamic range is 20% larger, do not demand Bessel functions algebraic sign correction algorithms and there is no singularities when the static phase shift between the interferometer arms is equal to an integer multiple of π/2 rad. Electronic noise and random phase drifts due to ambient perturbations are taken into account in the analysis of the method. The XY nanopositioner characterization was based on the analysis of linearity between the applied voltage and the resulting displacement, displacement frequency response and main resonance frequencies determination.