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Reverse your smart energy meter with this simple trick!
coppice:
--- Quote from: Jeroen3 on August 17, 2021, 06:35:52 am ---From what I know, most energy meters lock the sampling rate to 64, 128 or 256 samples per cycle.
A way to do this, though I'm not sure if this is the way it is actually done, is to oversample royally, then decimate to your required samples per cycle.
This ensures all further calculations, like power and reactive power, are done with the same phase error free stream.
However, that is only the sampling, the power units calculation is another subject. Different methods, different speeds and errors.
https://www.mdpi.com/1996-1073/13/17/4322
--- End quote ---
I don't know of any energy measurement front end for a consumer meter which locks the frequency of the ADC sampling to the mains. They all sample at a fixed rate, and calculate at the same rate. What you are describing sounds like the design of a power quality monitor. Most of those process synchronised samples, typically at 256 samples per mains cycle these days. However. most modern designs don't actually run their ADCs synchronously with the mains. They let them run at a fixed rate, and then digitally resample to a precise power of two multiple of the prevailing mains frequency. Then they can perform things like FFTs without worrying about windowing effects, which can really hurt accuracy when you are trying to measure to 0.1% or better. They work out the exact mains frequency by analysing the raw sampled stream, and continuously adapting as the frequency of the mains, or their own raw sample clock, might drift with time.
Alti:
--- Quote from: Zero999 on August 16, 2021, 06:09:00 pm ---I wonder if spread spectrum sampling would help?
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I think that the knowledge about exact moment of when ADC is sampling, for the purpose of tampering the measurement results, has minimal practical value. It might be advantageous when the disturbance is at about similar frequency as sampling but when the disturbance is tens or hundreds of times faster then what difference that might be? The meter is not going to notice that upper part of BW anyway.
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