[ICanHas]

But your claim that "Additionally, with nonlinear loads, a multimeter must have DSP in order to measure properly." is wrong. There is no conversion to analog. Are you just parroting? The four quadrant real time true power converter provides analog output proportional to real-time watt. There is an apparatus called an integrator which takes the real time true watts information and continuously output the result as an analog signal, which can then go into A/D converter for display reading. Integration is a the process used for averaging.

NHM,
The width of averaging frame is continuously moving forward or it can be anchored down at the starting point and expand continuously. The width is known by the mathematical technical term call the limits of integration. The operating characteristics of integration can be changed with a device such as a potentiometer, an analog apparatus that can vary the resistance by turning the shaft, which then analogly tell the integrator what to do without the quirkiness or lag of digitally cheapened digital PIC software driven microcontroller.

Those cheapo China sourced sampling meters are good under limited conditions and provide pretty good accuracy over a narrow operating envelope.

I think NHM has financial interest ties in pushing open source hardware coupled with royalty costing software.

Analog data is difficult to use for further analysis, so good instruments use a combination of analog front end with digital back end. Analog watt converters and integrators work continuously and produce accurate result even if the load behavior changes every wave cycle or the frequency tend to fluctuate.

With high performance analog front end with digital chart recorder, you can change the sampling rate on chart recorder as needed but real time wattage is always available. This ain't the case with those digital crap.

Plot out the cumulative joules consumed by the motor during the start-up cycle, and the instantaneous power from 0 second until reaching 3450rpm 0.25 seconds later.

Many devices use standby power in bursts and this type of use is also difficult for cheap sampling based devices.

To say "must have DSP" is ludicrous when it is just one of the ways of doing it especially when analog front-end has superiority in many ways. The absolutely the worst one in terms of real time reporting and latency is the virtual DSP that is based on program code... the kind you like to push.

Works good for a steady slow responding loads, but they totally suck for real time for unstable voltage, frequency and wildly varying loads or when you need power reading in real time, such as power input during acceleration or sudden motor loading.