I've got an office with some servers on a UPS. From time to time, the
UPS is reporting issues with the mains power quality and switching to
battery. It then typically switches back soon after, but sometimes the
RCBO for that circuit trips at the same time.

I'm looking for something that can monitor the power quality, so I can
try to isolate the problem. Does anyone know of monitoring equipment
that can monitor the quality of mains power over a period of time? I
guess something that just measured voltage would be a start.

I've got a multimeter, but it only shows the instant reading and can't
record data. And these events only occur once a week or so, and seem
to be random.