dears,

some time ago that thread (http://www.8052.com/forum/read.phtml?id=71354) was started by a colleague that wanted to log periods of power outage.

I was thinking in something simmilar: logging occurrencies of power outage (not when, but how many times, the total time and the largest period without power) and, since I'm logging, why not record the maximum, minimum and average values from the AC power in a given period?

sounds easy... the problem is the minimum power... if there is a power outage the recorded value will be 0V, but I want the minimum when there is power...

another thing: I'm rectifing and filtering the AC and measuring the resulting DC power, when there is a power outage the capacitor starts discharging and messes my reading.

Ideas that I had: discard the measurement if the reading is below some value (eg. 70V), but it can happen during the discharge time, so I'll log 100V, 90V... check, before logging, if there is power, like some relay that will open if the power fails, so I start logging the duration of outage.

the realy idea seems easy, but since we are talking about a micro-controlled circuit the power can fail AFTER I read the realy and I'll have some funny reading...

by the way, all the problems above can mess with the calculation of average AC power...