In article ,
John Rumm writes:
wrote:
I'm afraid I don't fully understand. A device consuming 20W will do so
irrespective of the power factor. A power meter should measure this
power, just as my electricity meter does. What does making allowances
for pf mean?

The simplest ones measure the line voltage and the current flow and from
that deduce the power consumption. On kit with non unity power factors
this will end up reporting the VA rating rather than the real power
consumption.

There's an even simpler one available which measures only current
(using a clamp-on current transformer), and assumes the mains voltage.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]