Like many dirty measurements, I find them interesting to interpret by watching them over time with my Arduino based SensorServer. I've found the voltage dips twice a day, around 5am and 5pm, independent of what I do. Have a look here:
I feed this with 12 vac output from a wall transformer. I step this down with a 2k/500 ohm voltage divider, rectify this with a signal diode and smooth with a .1 capacitor in front of an Arduino analog input.
+----|>|-----------+-----o to ADC | | o---/\/\/\---+---/\/\/\---+ --- 12vac 2k 500 | --- .1 | | o-------------------------+-----+-----oI calibrated this by comparing the ADC to reference measurements made with a Fluke digital volt-meter. I took samples with and without my space heater on so as to bracket a range of values. I fit this data to a linear curve to arrive at this formula:
volts = adc * 0.1397 + 5.5.The 5.5 offset is presumably due to the diode drop, magnified by the fact that it operates in a voltage-scaled portion of the circuit.
Whole House Power Consumption
I would like to measure my whole house power consumption with high resolution in time and watts. I notice that my power company, PortlandGeneralElectric, is already doing so with a "smart" power meter from Sensus:
I've written to Joel hoping to get access to some of the data he has collected. Until then, I'm measuring my power consumption by periodically clipping a RadioShack ac ammeter around the big wires in my breaker box.
I've found, for the whole house:
|Last edited February 28, 2010
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