# measuring phase difference in 3 phase power

For my ceramics oven I had 3 phase power installed. But power consumption according to the meter is way higher than the nominal 7KW the oven consumes. A friend told me that if the phase (or sinus) is not in sync there is a negative current causing the meter to run awry. For firing 3 to 4 times my oven during 8 hours per month and consume over 1000KWh seems to be a bit too much. A Pi already takes care for the firing process, so I want to measure power consumption AND to visualise the 3 sinusoides on my screen so I can see for myself if there is something that needs to be corrected if things become out of phase. When possible do that in Python, accompanied with the proper libraries of course, like mathlib or numpy and gnuplot and so.

• Welcome to Raspberry Pi :-) But your question is too broad and opinion based. Such questions are flagged and may be closed. This site isn't made for brainstorming and discuss general issues. It is made to do one specific question that can be answered detailed. Please take the short Tour and visit the Help Center to get an idea how things work here. – Ingo Apr 21 '19 at 18:25

Question

Problem - 3 phase 7 kW ceremics oven meter not accurate, possibly out of phase sync negative current driving meter crazy.

Current situation - Rpi already doing firing job OK.

Question - How to visually display and plot three phrases on screen using python libraries

Well, the tricky part is the AC current sensing hardware. There are various cheapy eBay and Amazon modules doing that. If you know how to get the phase data, then it is easy to find python and maths libraries to do the data logging and analysis.

A quick and dirty get around is to borrow a phase meter from you friend, or buy him a beer, ... :)

Three Phase Digital Phase Volt-Ampere Meter RS232 Interface - \$626

Phase range 0° ~ 360°, LCD display, 240 × 160 dots

RS232 to provide the convenience for data analysis and management

Update 2019apr22hkt1131

Displaying and measuring home mains 200VAC one phase voltage with a cheapy handheld scope.

All these years I have been using a cheap (US\$100 10 years ago, now US\$200!) hand held scope to check my home mains voltage. From time to time, the mains voltage has glitches casusing my PC to reset unexpectedly, or the lamps flickering. So I use the scope to USB transfer the AC voltage picture to my Windows PC, then show it to the power company, complaining that their electricity is dirty, ... :)

So perhaps your oven meter is not driven crazy by out of sync phase negative current, but by dirty mains lines, ... :)

UNI-T UT81B LCD Handheld Digital Multimeter USB LCD Meter Tester Oscilloscope - US\$194