Last Friday I was tinkering with apcupsd and rrdtool and decided to join both: I’d monitor the mains voltage during a period of 24 hours, to see if it varied during the day. Well, apparently, it does.
To my untrained eye it looks like it varies with the load in the electric network: the voltage is at its highest during nighttime, and hits its lowest point at 13:30 (solar mid-day in Galicia); then rises again while people is having lunch then dips until after 18:00. The discontinuity at about 20:15 was due to my briefly stopping apcupsd to change a configuration in my UPS.
Now, I don’t know if the mains voltage really varies so much during the day or if it is because my UPS’s voltmeter is a piece of shit (which it, apparently, is) and is affected by the presence of non-resistive loads or whatnot, but the graph is interesting anyhow. Detailed explanations by people who know more about electricity than yours truly will be appreciated.
On an unrelated subject, I’m teaching myself how to juggle a reverse cascade. To do it properly, it requires better timing and more homogeneous throws than I’m currently able to do. So, to master it, I first need to suck less at juggling. We’re working on it.