In uk.d-i-y, Ian Stirling wrote:
I'm fairly confident that most of these devices have a single channel
8 bit A/D (minimum current is typically 40mA = 13000mA/256), sampling at
400Hz or so. (or maybe 50Hz, with undersampling, I'm not sure.)

Add a 4 bit micro, and an LCD, and you've got a power meter.

A 0 power factor device can have a very spiky current draw.
My PC power supply draw looks like a sharks fin, with a very sharp rise, and
a slow decay to a fast fall.

Presumably if you measured total energy consumption over a long period,
things would even themselves out. But how long, I wonder? My Maplin
meter stops at 9999 kWh.

--
Mike Barnes