Mike Barnes wrote:
In uk.d-i-y, wrote:
Mike Barnes wrote:
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.)
snip
If the draw looks like a sharks fin, then the instantaneous reading
*will* vary won't it? Unless the sample times are synchronised to the
wave form.

With my observations, it diddn't, but was consistent within a range of
voltages (about +-2%) and with a 1.8 ohm resistor wired into the mains lead.

Never mind. I'm quite happy to believe that the readings are unreliable
for PC power supplies etc.