On Mon, 19 Aug 2013 18:26:52 +0100, MrWeld wrote:

On 19/08/2013 12:19, Caecilius wrote:
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.

A really DIY approach would be to feed the output of mains transformer,
possibly via a potentiometer, into the audio line-in socket of a PC. A
wall-wart with an AC output (rare, but they do exist) would probably
satisfy most safety concerns. You could record the waveform with audio
software of your choice, presumably at a fairly low sampling rate. I'm
not sure whether a typical integrated soundcard can go as low as 50Hz
though.

I'm not sure how well very fast transient spikes would pass through a
mains transformer with its large number of turns and magnetic properties
that obviously favour mains frequency.

A divider that consists of resistors only would provide an accurate view
of the situation, but safety and isolation could then be a problem.