i bought one about 2 years ago, new in the box off an ebay seller that had jillions of them
i then set about googling the darn thing to find out how to use the thing to do what i wanted, and found that they are capable of accurately measuring over 300 parameters. literally everything one can imagine it can measure, store and display.
the front screen can display about 6 parameters that you can easily toggle through, and another dozen or so you can toggle through with a magnet over an internal read switch,
the really cool thing is you can press an internal switch and put it in calibration mode
and measure right down to watt/hrs with very good resolution. this is incredibly useful in doing BSFC testing of generator sets at various loads.
that internal switch requires taking the globe off to access which is a problem, but being "lexan" (plastic) i simply drilled a small hole through the front to access it with a short piece of wire (drill bit) which allows me to reset the meter head into calibration mode.
i found there is a company in north carolina iirc that can program the head to read out exactly what you want to monitor, again the limit is about 6 parameters on the front screen and another dozen or so with a magnet over the reed switch.
there are also option cards available that either open or close a set of contacts if any programmed parameter is out of spec, things like over/under voltage, over/under frequency etc.
the front screen also has a neat little led direction arrow that tells you whether your system is taking power from the grid or putting power back to the grid, a nice addition to
a very cool meter head.
i bought a combination meterbox/breaker panel, it is good for 100amps split phase
and has iirc 6 breaker (squareD Q series), i paid 34 bucks for the box at home depot.
this thing enabled me to quit using clamp on amp meters, along with separate voltmeters and all the other instrumentation, because this puppy does it all, and much more accurate and safer as well.
other things i use it for is measuring power factor, harmonic distortion, amps, volts, watts, watt/hrs, instantaneous or peak watts and amps, cummulative kwatt/hrs, and watt/hrs, and a plethora of other interesting stuff.
bob g