I´d like to ask you for help. I have done energy meter with 3 phase ADE7758 chip. Everything working fine (SPI communication, etc.) but except one thing. When I want to measure power and other values of electric fan heater (2kW) I get into strange situation. Sometimes when I turn it on or off I get high values from ADE7758 registers or zero values. Sometimes it causes drop of all measuring ADE7758 board.
I tried to isolate the problem so I disconnect all three current transformers but the problem still persists. That means the problem (interference/noise or peak) goes to my measuring board through the voltage input.
I followed all recommendation during the board conctruction -
1) Antialising filter and ferrite bead on all inputs
2) Separated AGND and DGND connected with ferrite bead in one point
3) Current transformers using DGND
4) I have optical isolator on SPI interface (because when the measuring and MCU board is connected directly it also cause fall down of MCU board)
5) I followed all recommended distances during the board design
One important think is when I connect mentioned fan heater not directly but through cca 20 meters of cable and turn it on/off and still repeating it I am not able to make drop of my measuring board. So the distance plays a big role (20 meters of cable is equal to some induction).
My question is how can I filtered it?
Thank you in advance for answer.