  In the present work we report recent radial electric field measurements
carried out with the Doppler reflectometry system in the TJ-II stellarator. The
study focuses on the fact that, under some conditions, the radial electric
field measured at different points over the same flux surface shows
significantly different values. A numerical analysis is carried out considering
the contribution arising from the radial dependence of $\Phi_1$ as a possible
correction term to the total radial electric field. Here $\Phi_1$ is the
neoclassical electrostatic potential variation over the surface. The comparison
shows good agreement in some aspects, like the conditions under which this
correction is large (electron-root conditions) or negligible (ion-root
conditions). But it disagrees in others like the sign of the correction. The
results are discussed together with the underlying reasons of this partial
disagreement. In addition, motivated by the recent installation of the dual
Doppler reflectometry system in Wendelstein 7-X (W7-X), $\Phi_1$ estimations
for W7-X are revisited considering Core-Electron-Root-Plasma (CERC) plasmas
from its first experimental campaign. The simulations show larger values of
$\Phi_1$ under electron-root conditions than under ion root ones. The
contribution from the kinetic electron response is shown to become important at
some radii. All this results in a potential variation size noticeably larger
than estimated in our previous work in W7-X \cite{Regana_nf_57_056004_2017} for
other plasma parameters and another configuration.
