Interested to see how voltage and things fluctuated during the course of a day, I decided to knock up a power quality monitor.
It turns out that it was fairly straight-forward. Find a pregnant plug with a plain old transformer and no rectifier/capacitors in it. Hook it up, via an appropriate potential divider, to the line-level input on the sound card. Use some software to do the fancy analysis (and compensate for the x-fi's dismal performance at bass frequencies).
Anyway, after a couple of hours of playing around, it looks like I have a vaguely working thing.
PowerThing.png
You can see how the voltage dipped when I turned on all 4 rings on my stove, and a bit later when I turned on my kettle. The 3100 W load of the kettle pulls down the mains voltage by a whole volt!
Other things that are interesting is the rather high level of harmonic distortion in the mains waveform. I'm not quite sure where it's coming from, or even if its artifactual - if it is an artifact, I really can't explain why - I've already corrected for the X-fi's low-frequency roll-off. What is odd, is that the distortion level drops when the load on the mains rises - I've no idea what this means, but if someone could shed some light, I'd be interested. At the bottom you can see a record of power frequency. You can see it going up and down in response to the balance of load and power generation increasing/decreasing.
Now, if I could find a suitable current transducer, I could make a kill-a-watt type device.
It turns out that it was fairly straight-forward. Find a pregnant plug with a plain old transformer and no rectifier/capacitors in it. Hook it up, via an appropriate potential divider, to the line-level input on the sound card. Use some software to do the fancy analysis (and compensate for the x-fi's dismal performance at bass frequencies).
Anyway, after a couple of hours of playing around, it looks like I have a vaguely working thing.
PowerThing.png
You can see how the voltage dipped when I turned on all 4 rings on my stove, and a bit later when I turned on my kettle. The 3100 W load of the kettle pulls down the mains voltage by a whole volt!
Other things that are interesting is the rather high level of harmonic distortion in the mains waveform. I'm not quite sure where it's coming from, or even if its artifactual - if it is an artifact, I really can't explain why - I've already corrected for the X-fi's low-frequency roll-off. What is odd, is that the distortion level drops when the load on the mains rises - I've no idea what this means, but if someone could shed some light, I'd be interested. At the bottom you can see a record of power frequency. You can see it going up and down in response to the balance of load and power generation increasing/decreasing.
Now, if I could find a suitable current transducer, I could make a kill-a-watt type device.