  White dwarf studies carry significant implications across multiple fields of
astrophysics, including exoplanets, supernova explosions, and cosmological
investigations. Thus, accurate determinations of their fundamental parameters
(Teff and log g) are of utmost importance. While optical surveys have provided
measurements for many white dwarfs, there is a lack of studies utilising
ultraviolet (UV) data, particularly focusing on the warmer ones that
predominantly emit in the UV range. Here, we present the medium-resolution
far-UV spectroscopic survey of 311 DA white dwarfs obtained with Cosmic Origins
Spectrograph (COS) onboard Hubble Space Telescope confirming 49 photometric
Gaia candidates. We used 3D extinction maps, parallaxes, and hydrogen
atmosphere models to fit the spectra of the stars that lie in the range 12 000
< Teff < 33 000 K, and 7 <= log g < 9.2. To assess the impact of input physics,
we employed two mass-radius relations in the fitting and compared the results
with previous studies. The comparisons suggest the COS Teff are systematically
lower by 3 per cent on average than Balmer line fits while they differ by only
1.5 per cent from optical photometric studies. The mass distributions indicate
that the COS masses are smaller by approximately 0.05 Msol and 0.02 Msol than
Balmer lines and photometric masses, respectively. Performing several tests, we
find that the discrepancies are either arising due to issues with the COS
calibration, broadening theories for hydrogen lines, or interstellar reddening
which needs further examination. Based on comparative analysis, we identify 30
binary candidates drawing attention for follow-up studies to confirm their
nature.
