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By "clamp" I presume you mean current transformer.

You can use 3 emonTx's, or 2 emonTx's plus your emonPi (if that is what your "Pi" is). That set-up will give you the most accurate measurement because you measure the voltage of all 3 lines to neutral.

However, if the voltages on the 3 lines are substantially the same, or you are prepared to accept some inaccuracy if they are not, then you can use the 3-phase sketch and the one emonTx you have bought to obtain a good estimate of the total power. (The 3-phase sketch works by saving the voltage wave and "replaying" it ⅓ and ⅔ cycle later to calculate the power in the second & third phases.) But you will need a programmer to upload and calibrate the new sketch, which is on GitHub.

hello,

thanks for the information - i bought the usb programmer with the emontx - i found the sketch but i'm not sure how to proceed.

i got the ide running and on the serial monitor (ide) - i receive data from the emontx - i tried to figure out from the website how to compile the provided files in https://github.com/openenergymonitor/ArduinoDue_3phase but could not.

so what should i do with the cpp and h file and the ino file?

just upload the ino file? and what should i do after the upload so that this new code is in place and used?

i have a bus system in my house and measure almost (but not all) all circuits - so on my bill i had this year a big difference - my own measurement was apx. 7000 kw/h but on the bill i have 10000 kw/h - so i want to use a pi and serial connection to the emontx and write the data every minute to my database where all the other data is stored as well - so i can compare what is the difference between all my monitored circuits and the circuits which are not part in my bus - so i can try to find which part is consuming that big amount of power.

thanks

holli