  Driven nanomechanical resonators based on low-dimensional materials are
routinely and efficiently detected with electrical mixing measurements.
However, the measured signal is a non-trivial combination of the mechanical
eigenmode displacement and an electrical contribution, which makes the
extraction of the driven mechanical response challenging. Here, we report a
simple yet reliable method to extract solely the driven mechanical vibrations
by eliminating the contribution of pure electrical origin. This enables us to
measure the spectral mechanical response as well as the driven quadratures of
motion. We further show how to calibrate the measured signal into units of
displacement. Additionally, we utilize the pure electrical contribution to
directly determine the effective mass of the measured mechanical mode. Our
method marks a key step forward in the study of nanoelectromechanical
resonators based on low-dimensional materials in both the linear and the
nonlinear regime.
