  The prevalent use of large volume liquid argon detectors strongly motivates
the development of novel readout and monitoring technology which functions at
cryogenic temperatures. This paper presents the development of a cryogenic CMOS
camera system suitable for use inside a large volume liquid argon detector for
online monitoring purposes. The characterisation of the system is described in
detail. The reliability of such a camera system has been demonstrated over
several months, and recent data from operation within the liquid argon region
of the DUNE 35tcryostat is presented. The cameras were used to monitor for high
voltage breakdown inside the cryostat, with capability to observe breakdown of
a liquid argon time projection chamber in situ. They were also used for
detector monitoring, especially of components during cooldown.
