Thanks for the clarification. My intention there was to calculate watt-hours and to convert that to BTU in the next step. Is this good enough to get a rough estimate?
I know it would be much better to have a data logger and do the measurements more frequently. I might do that at some point, but I am mainly interested in seeing if my results warrant the additional investment of time and money. Thanks again for your comments and I also wonder if you would think these results merit further experimentation. On Mon, Oct 15, 2012 at 9:05 AM, Abd ul-Rahman Lomax <a...@lomaxdesign.com>wrote: > At 06:28 AM 10/15/2012, Jack Cole wrote: > > Input power. >> >> W = ((Amperage at Time 1 + Amperage at Time 2) / 2) * ((Voltage at Time 1 >> + Voltage at Time 2) / 2) * (Minutes in interval / 60) >> > > You are going to go nuts if you don't keep your units straight, and don't > keep in mind the difference between power and energy. > > The forumula you give calculates average power for an interval (Time2 - > Time1), then multiplies it by the time in hours, presumable to get > watt-hours, not watts. Watt-hours are a measure of energy. > > That's not generally correct, because the energy is the integral of the > power over time, not the product of the average energy and the time. > > If the current has no significant AC component, and you measure voltage > and current frequently, you can sum the product in a spreadsheet. Otherwise > it gets really complicated. > > In a standard CF experiment, the voltage/current measurements might be > once per minute. Or in more sophisticated experiments, the measurements > might be more frequent than that. >
