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Smart meters

Kelly Marie Angel

Hi about 3 weeks ago I was forced into having a smart meter they needed to replace the gas meter because it was in a dangerouse state fair enough I won't argue about that. But they also changed my electric meter now I've just measured the current in the phase tail to the meter and it works out as about 200mA more than the calculations  based on my wattage consumption ie watts divided by 240 should give amps now is the 200ma likely to be the meters consumption or just something with a less than unity PF? Also do smart meters measure kilowatthours like a proper meter or do they measure KVarh 

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    I was under the impression that the simplest way to do a watt-hour meter was to sample the I and V as quickly as your ADCs will go, multiply the instantaneous I by the instantaneous V to get instantaneous P, then sum the instantaneous P's all together over a second, and divide by your sampling rate.

    Indeed. I'll have to dig a bit deeper into the firmware code to see exactly what's happening. I know the system can also be used without a voltage reference (just presumes say 240V r.m.s. instead) so perhaps it's been written from that point of view, or it just might be a limitation of the hardware.

    I the meantime I think I'll take Mike advice and try to get my hands on a 'scope to see what's really happening waveform-wise.

        - Andy.

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  • 0

    I was under the impression that the simplest way to do a watt-hour meter was to sample the I and V as quickly as your ADCs will go, multiply the instantaneous I by the instantaneous V to get instantaneous P, then sum the instantaneous P's all together over a second, and divide by your sampling rate.

    Indeed. I'll have to dig a bit deeper into the firmware code to see exactly what's happening. I know the system can also be used without a voltage reference (just presumes say 240V r.m.s. instead) so perhaps it's been written from that point of view, or it just might be a limitation of the hardware.

    I the meantime I think I'll take Mike advice and try to get my hands on a 'scope to see what's really happening waveform-wise.

        - Andy.

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