Calibration and USA mode issue

Hello, few days ago I bought an EmonTX V3.

The voltage in my country is 120v. When I connected my EmonTX V3, I noticed that it was measuring above the real (122.4v) when in my multimeter it was measuring 119.8v / 120.2v. I proceeded to calibrate the firmware (emonTxV3_RFM12B_DiscreteSampling) of my EmonTX to get something more real.

Before calibrating the EmonTX, I was receiving a difference of 2kWh / 3kWh per day versus my street meter.

After the calibration, I can note that the difference is still more than 2KWH per day.

What else can I do in order to reduce my difference?

My installation:

My EmonTx USA Mode:



Robert Wall's picture

Re: Calibration and USA mode issue

Have you done the full calibration procedure? There are the current inputs too that affect the power and energy calibration. What is 2 kWh as a percentage of your daily energy consumption? And how accurate is the voltage balance between the two legs of your supply?

servandob's picture

Re: Calibration and USA mode issue

Hi Robert,

Everyday I consume more or less 24kWh and my EmonCMS reported that I consumed 26 or 27 kWh.


Robert Wall's picture

Re: Calibration and USA mode issue

You've set the voltage calibration so that the emonTx shows the same as your multimeter - is that correct? And you're still about 10% out? The current could account for 4% worst case, so I must ask whether your voltage measurement is in fact correct, and the median of the two legs of your supply?

Have you got any appliances that switch rapidly, like an induction hob? The reason for asking that is, if by chance the discrete sample sketch samples every time the load happens to be on, it will read high. The 'continuous' sketch should solve the problem if that's the case, but it will be better to eliminate calibration errors first.

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