Slashdot Mirror

They measure the power at the wall and not on the CPU specifically, so there's no 'fraud' going on. Putting processing elements on the north bridge does nothing to gain this system an advantage. Reading the contest rules, they recommend power meters like this: http://www.brandelectronics.com/meters.html

I did my undergrad thesis in home power metering, and used 2 different models of Brand power meters. They sample current and voltage at 4kHz to accurately measure true power factor (see their description). Single circuit "plug-through" meters are $150-350; the higher-end ones have computer connectivity and datalogging.

Another option for those interested in exploring home power use--and not ignoring power factor--is the Watt's Up? meter (also plug-through, $100-150, with computer connectivity at the high-end). I believe both this and the Brand meter will show you the instantaneous power factor of the load you're metering if you cycle through the display.

While power factor might be irrelevant for simple inductive loads, I agree with the parent that this is an oversight (if it's true that the hardware in question doesn't do more than measure volts * amps), particularly if you want to check usage against your power bill. Power factor is more of issue for commercial electricity customers, who are billed for non-unity power factor and often install huge banks of capacitors to correct it (though i forget exactly how this helps).

I did my undergrad thesis in home power metering, and used 2 different models of Brand power meters. They sample current and voltage at 4kHz to accurately measure true power factor (see their description). Single circuit "plug-through" meters are $150-350; the higher-end ones have computer connectivity and datalogging.

Another option for those interested in exploring home power use--and not ignoring power factor--is the Watt's Up? meter (also plug-through, $100-150, with computer connectivity at the high-end). I believe both this and the Brand meter will show you the instantaneous power factor of the load you're metering if you cycle through the display.

While power factor might be irrelevant for simple inductive loads, I agree with the parent that this is an oversight (if it's true that the hardware in question doesn't do more than measure volts * amps), particularly if you want to check usage against your power bill. Power factor is more of issue for commercial electricity customers, who are billed for non-unity power factor and often install huge banks of capacitors to correct it (though i forget exactly how this helps).

The Power Meter the guy mentions in the article is exactly the sort of thing I'd planned to build myself to figure out how much electricity my various electronics consume. I'd planned to do it with a Radio Shack multimeter (that includes current reading) that I'd splice into a little extension cord. But... It would be awesome if there was a relatively inexpensive product that'd do the same. Anyone seen one? The cheapest option from the company he mentions costs $150.

I recommend the Brand meter. See my other post on this topic for more details and other meters to use for the same purpose.

The high-end Brand meters can also connect to a PC via RS-232 serial (Win 95/98 only) and log data that way, and there is even a model with non-volitile memory and a datalogger onboard, so that you can plug in your fridge and come back in a month and download its power consumption history. I highly recommend these meters, since they don't simply measure Watts as Volts * Amps, but calculate an implicit power factor by sampling instantanious Volts (this is a sine wave in AC, remember) & Amps at 4 kHz in order to measure your power consumption just like your utility does.

For more & larger loads, check out the Brand "One Meter" which can handle 120 or 240 V AC loads, DC loads, and 64 channels simultaniously. Sensors are networked to the datalogger via Cat-5 (not over TCP-IP, though). There is a small LCD for instantanious readout, and it can download data through any com program and a serial cable (I use Win 2k, never got it to work with my Mac).

One of the coolest devices I've seen is the WebDAQ which is a 32-channel datalogger with built-in server; just plug in some sensors and an ethernet network, and you can view data live over the web! A little pricey for me at $1k, but cheaper than putting together the pieces.

The high-end Brand meters can also connect to a PC via RS-232 serial (Win 95/98 only) and log data that way, and there is even a model with non-volitile memory and a datalogger onboard, so that you can plug in your fridge and come back in a month and download its power consumption history. I highly recommend these meters, since they don't simply measure Watts as Volts * Amps, but calculate an implicit power factor by sampling instantanious Volts (this is a sine wave in AC, remember) & Amps at 4 kHz in order to measure your power consumption just like your utility does.

For more & larger loads, check out the Brand "One Meter" which can handle 120 or 240 V AC loads, DC loads, and 64 channels simultaniously. Sensors are networked to the datalogger via Cat-5 (not over TCP-IP, though). There is a small LCD for instantanious readout, and it can download data through any com program and a serial cable (I use Win 2k, never got it to work with my Mac).

One of the coolest devices I've seen is the WebDAQ which is a 32-channel datalogger with built-in server; just plug in some sensors and an ethernet network, and you can view data live over the web! A little pricey for me at $1k, but cheaper than putting together the pieces.

The high-end Brand meters can also connect to a PC via RS-232 serial (Win 95/98 only) and log data that way, and there is even a model with non-volitile memory and a datalogger onboard, so that you can plug in your fridge and come back in a month and download its power consumption history. I highly recommend these meters, since they don't simply measure Watts as Volts * Amps, but calculate an implicit power factor by sampling instantanious Volts (this is a sine wave in AC, remember) & Amps at 4 kHz in order to measure your power consumption just like your utility does.

For more & larger loads, check out the Brand "One Meter" which can handle 120 or 240 V AC loads, DC loads, and 64 channels simultaniously. Sensors are networked to the datalogger via Cat-5 (not over TCP-IP, though). There is a small LCD for instantanious readout, and it can download data through any com program and a serial cable (I use Win 2k, never got it to work with my Mac).

One of the coolest devices I've seen is the WebDAQ which is a 32-channel datalogger with built-in server; just plug in some sensors and an ethernet network, and you can view data live over the web! A little pricey for me at $1k, but cheaper than putting together the pieces.